So I'm relatively new to Android and trying to build a Camera App. But I'm allready stuck with catching the Camera IDs.  I have my public CameraManager, a public String array and a public TextView and I was just trying to get the CameraIDs from my CameraManager and display the first of my IDs in my textview. And the App builds without errors but as soon as I try to execute it on my phone, it just crashes. Where is my mistake?  public CameraManager mCamera; public String[] cameraIDs; public TextView text = (TextView)findViewById(R.id.text);   And in my onCreate function:  try {     cameraIDs = mCamera.getCameraIdlist();     text.setText(cameraIDs[0]); } catch (CameraAccessExeption e) {     text.setText("Sorry, couldn't find camera device."); }   And, as requested, the error log from my phone:  java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.test/com.example.test.ThrowActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.Window$Callback android.view.Window.getCallback()' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2360) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2509) at android.app.ActivityThread.access$1000(ActivityThread.java:153) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1373) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:154) at android.app.ActivityThread.main(ActivityThread.java:5527) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:739) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:629) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.Window$Callback android.view.Window.getCallback()' on a null object reference at android.support.v7.app.AppCompatDelegateImplBase.<init>(AppCompatDelegateImplBase.java:117) at android.support.v7.app.AppCompatDelegateImplV9.<init>(AppCompatDelegateImplV9.java:149) at android.support.v7.app.AppCompatDelegateImplV11.<init>(AppCompatDelegateImplV11.java:29) at android.support.v7.app.AppCompatDelegateImplV14.<init>(AppCompatDelegateImplV14.java:54) at android.support.v7.app.AppCompatDelegateImplV23.<init>(AppCompatDelegateImplV23.java:31) at android.support.v7.app.AppCompatDelegate.create(AppCompatDelegate.java:200) at android.support.v7.app.AppCompatDelegate.create(AppCompatDelegate.java:183) at android.support.v7.app.AppCompatActivity.getDelegate(AppCompatActivity.java:519) at android.support.v7.app.AppCompatActivity.findViewById(AppCompatActivity.java:190) at com.example.test.ThrowActivity.<init>(ThrowActivity.java:26) at java.lang.Class.newInstance(Native Method) at android.app.Instrumentation.newActivity(Instrumentation.java:1068) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2350) ... 9 more   line ThrowActivity.java:26  public TextView text = (TextView)findViewById(R.id.text);

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


In class our teacher told us that, if a Lagrangian contain $\ddot{q_i}$ (i.e., $L(q_i, \dot{q_i}, \ddot{q_i}, t)$) the energy will be unbounded from below and it can take any lower values (in other words be unstable). In this type of systems can we show that the energy is conserved ? Or in such system does energy conservation is applicable ?

Is there a way of explaining why no differential equations in physics exceed order two without delving into Lagrangian and Hamiltonian mechanics - i.e. from Newtonian mechanics? Moreover, is there such an alternative proof, which focuses more on physical reasoning than abstract mathematics?


Since $n!$ represents $$1\cdot2\cdot3\cdots n,$$ I am wondering if there is a way to represent  $$1+2+3+\dots+n?$$ What are some usual notations for the computation of some common sequences? Any other examples?

(Pardon if this seems a bit beginner, this is my first post in math - trying to improve my knowledge while tackling Project Euler problems)  I'm aware of Sigma notation, but is there a function/name for e.g.  $$ 4 + 3 + 2 + 1 \longrightarrow 10 ,$$  similar to $$4! = 4 \cdot 3 \cdot 2 \cdot 1 ,$$ which uses multiplication?   Edit: I found what I was looking for, but is there a name for this type of summation?


Question statement: Let $F(x,y,z)$ is a continuously differentiable function with nonvanishing partials at $(0,0,0).$  Define $x = x(y,z), \; y = y(x,z), \; z = z(x,y)$ as the solutions of the equation $F(x,y,z) = F(0,0,0)$ in the neighborhood of $(0,0)$ in the corresponding variables.  Prove that  $$\bigg(\frac{\partial x}{\partial y}\bigg) \bigg(\frac{\partial y}{\partial z}\bigg)\bigg(\frac{\partial z}{\partial x}\bigg) = - 1,$$ where  the  three partial  derivatives  are  taken at  point $(0,0)$  in  the corresponding pair of variables.    I know I have seen a couple weak proofs of this, one in thermodynamics where my professor referred to this as "The -1 Rule", and another in the back of a long lost textbook of mine.  However, I am interested in a detailed, unshakable proof of this explicitly using the implicit function theorem.  I've tried several times now and I have been unable to produce one.  Any helpful comments/answers would be appreciated!

Ok guys, continuing my passage through edwards... here is the question... thanks for hints/solutions in advance:  Suppose $f(x,y,z)=0$ can be solved for each of the three variables $x,y,z$ as a differentiable function of the other two. Then prove that  $\displaystyle \frac{\partial x}{\partial y} \frac{\partial y}{\partial z} \frac{\partial z}{\partial x} = -1$  Verify this is the case for the ideal gas equation $pv =RT$ where (where $p,v,T$ are the three variables and $R$ is the constant).


I am trying to increase the size of the legend such that it exactly fits to size of the plot. But even after having a look at the PGF manual I could not figure out how I can realise my plan. Afterwards I want to equally distribute the legend entries within the box.  UPDATE  The actual solution was:  \def\WIDTH{7cm} \def\INNERSEP{3pt}  \begin{axis}[     xmin=1, xmax=10, xtick={1,...,10}, xmajorgrids=true, xlabel={Cores},     ymin=0, ymax=100, ymajorgrids=true, ylabel={MFLUPS/s},     scale only axis,  % <==== !!!!!!!     extra description/.code={         \node[         draw,         text depth=0pt,         at={(current bounding box.north-|current axis.north)},         anchor=south,         text width=\WIDTH-2*\INNERSEP,         inner sep=\INNERSEP,         outer sep=0pt,         ] {     \hbox to \linewidth{%         \hfill \ref{A} A \hfill \ref{B_B} B \hfill         }%     }; }, ]        \documentclass{standalone}  \usepackage{tikz}  \usepackage{pgfplots} \pgfplotsset{compat = newest}  \begin{document} \pgfplotsset{width=7cm} \begin{tikzpicture}  \begin{axis}[     xmin=1, xmax=10, xtick={1,...,10}, xmajorgrids=true, xlabel={Cores},     ymin=0, ymax=100, ymajorgrids=true, ylabel={MFLUPS/s},     legend style={         at={(current bounding box.north-|current axis.north)},         anchor=south,         legend columns=-1,         outer sep=0     }] \addplot [mark=square*, mark options={solid}, thick] table { 1   10 2   20 3   30 4   40 5   50 6   65 7   70 8   80 9   90 10  95 }; \addlegendentry{Graph A} \addplot [mark=*, mark options={solid}, thick] table { 1   10 2   20 3   25 4   40 5   25 6   65 7   70 8   25 9   90 10  95 }; \addlegendentry{Graph B} \end{axis} \end{tikzpicture} \end{document}

I am trying to customize the legend for this graph. First of all, I would like the legend width to be equal to the x-axis width. At the moment, I am setting the width of the legend via      /tikz/every even column/.append style={column sep=1.0cm}   and I could manually adjust this value so that length equals the x-axis width, but I guess that there is a more elegant way to set the width of the legend.  Second, I don't really like the little color rectangles in the legend. I only want one rectangle in front of every entry and not two. This rectangle does not need to have a border and should be vertically centred with the text. The alignment seems to be okay for the rectangle closer to the text, but not for one the far left.   Update: Thanks to Christian Feuersänger's comment, there is possibility to change the rectangles via   legend image code/.code={%     \draw[#1, draw=none] (0cm,-0.1cm) rectangle (0.6cm,0.1cm);   or what Gonzalo Medina proposed  legend image code/.code={%     \draw[#1, draw=none, /tikz/.cd, bar width=3pt, yshift=-0.2em, bar shift=0pt] %     plot coordinates {(2*\pgfplotbarwidth,0.6em)};   Third, I would like to the legend entries to start next to the text "Legend:".  I don't really know if with these requirements it still makes sense to use legend or if it would be better to add everything manually via after end axis/.code and \ref{label}.  Graph    MWE  \documentclass{article} \usepackage{pgfplots} \pgfplotsset{compat=newest}  \begin{document} \begin{tikzpicture}     \begin{axis}[                 ybar,                 height=6cm,                 title={Some plot},                 width=12cm,                 axis on top,                 y axis line style={opacity=0},                 axis x line*=bottom,                 tick align=inside,                 tick style={draw=none},                 xtick=data,                 ymajorgrids,                 major grid style={draw=white},                 xtick={1,2,3,4},                 legend style={                     at={(0.0,-0.15)},                     anchor=north west,                     legend columns=-1,                     /tikz/every even column/.append style={column sep=1.0cm}                         },             ]                    \addlegendimage{empty legend}             \addlegendentry{\textbf{Legend:}}                                \addplot coordinates {                 (1, 0.2064)                 (2, 0.3961)                 (3, 0.5961)                 (4, 0.7961)}; \addlegendentry[text width=45pt, text depth=]{legend a}             \addplot coordinates {                 (1, 0.3064)                 (2, 0.4961)                 (3, 0.6961)                 (4, 0.8961)}; \addlegendentry[text width=65pt, text depth=]{lengend b}     \end{axis}  \end{tikzpicture} \end{document}


Suppose $f: U\to V$ is a $C^1$ surjection from a $k$ dimensional manifold $U$ onto a $k$ dimensional simply connected manifold $V$ with everywhere nonzero Jacobian or nonsingular differential. Is $f$ diffeomorphic?

Does there exist a surjective immersion $\mathbb{R}^2 \to \mathbb{R}^2$ which is not a diffeomorphism?  I tried to modify $\exp: \mathbb{C} \to \mathbb{C}$ to be surjective, but I find it hard to preserve the property of being immersion.  I also noticed that if we replace $\mathbb{R}^2$ with $S^2$ or any other compact simply connected manifold, no such immersion exists, because then it would be a covering map (as a local diffeomorphism from compact space, thus proper), but since the manifold is simply connected, it must be a diffeomorphism.


Good afternoon to you all. My question is perhaps a simple one. Say I have a webserver running (Linux + Apache) I have a few domains I'd like to point to this machine. all great and dandy BUT! Do I need a dns server like BIND to be running as well? or can I just host multiple websites using just apache and the virtual hosts? thanks guys!

This is a  about whether to outsource DNS resolution for ones own domains   I currently have my ISP providing DNS for my domain, but they impose limitations on adding records. Therefore, I am thinking about running my own DNS.  Do you prefer to host your own DNS, or is it better to have your ISP do this?  Are there alternatives which I can look into?


Okey, lets beggin from a helpfull proposition I've already proved:  $$$$ if $a_i\equiv b_i\:\forall 0\le i\le m$ then to any $m$ numbers: $p_1,p_2,...,p_m\in \mathbb{Z}$  $$\sum _{i=0}^m\left(k_ia_i\right)=\sum _{i=0}^m\left(k_ib_i\right)$$  Now, what I want to prove, is: for number $x$ who's digits are: $x_m...x_0$  $$x\equiv 0\left(mod\:3\right)\:\:<==>\:\:\sum \:_{i=0}^m\left(x_i\right)\equiv 0\left(mod\:3\right)$$ $$$$ I guess the same exmaple with modulo 11 is the same proof.  So, in the first direction, we'll treat $\sum \:_{i=0}^m\left(x_i\right)\equiv 0\left(mod\:3\right)$ as given data and we'll prove $x\equiv \:0\left(mod\:3\right)\:$  That direction of proof is simple: As to the first proposition, we'll take $k_0=10^0,\:k_1=10^1,...,\:k_m=10^m$ and accroding to it: $$\sum \:\:_{i=0}^m\left(x_i10^i\right)\equiv \:\sum \:\:_{i=0}^m\left(0\cdot \:10^i\right)\left(mod\:3\right)$$ then also $$\sum \:_{i=0}^m\left(x_i10^i\right)\equiv 0\left(mod\:3\right)$$ As we want.  Now, in second direction, i have a little trouble: Now we are given: $x\equiv \:0\left(mod\:3\right)\:$ and we want to prove: $$\sum \:_{i=0}^m\left(x_i\right)\equiv 0\left(mod\:3\right)$$  So, from the data that is given we can conclude that: $$x=\sum \:\:_{i=0}^m\left(x_i\cdot 10^i\right)\equiv \:0\left(mod\:3\right)$$  And from here I dont sure how to get rid of the $10^i$, because the first proposition as i understand doesnt work on both directions (am I wrong?), because if n is a devider of a sum, we dont know for sure if it devides every element or only the sum of it, it can be the second case either.   So how do I show that $$\sum \:\:_{i=0}^m\left(x_i\cdot 10^i\right)\equiv \:0\left(mod\:3\right)\:\:\:===>\:\:\sum \:\:\:_{i=0}^m\left(x_i\right)\equiv \:\:0\left(mod\:3\right)$$

Here is the proof of the converse:  Iff a number $n$ is divisible by $3$, then the sum of its digits is also divisible by $3$.  Proof:  We know $n \mod 3 = 0$. By the basis representation theorem, $n$ can be re-written as $n_k10^k + n_{k-1}10^{k-1} + \cdots + 10n_1 + n_0 \equiv 0 \mod 3$. By the modular arithmetic addition rule, we can take $n_k10^k \mod 3 + n_{k-1}10^{k-1} \mod 3 + \cdots + 10n_1 \mod 3 + n_0 \mod 3$. But then we just get $n_k + n_{k-1} + \cdots + n_1 + n_0$, since $10 \mod 3 \equiv 1$.   Now suppose that the sum of the digits was divisible by 3. How can I prove that the representation in base $10$ is divisible by $3$?


I have no idea what cyclotomic polynomials are and how we can get the result using that. Is there another way to prove it? Any hint is appreciated.

I studied the cyclotomic extension using Fraleigh's text.   To prove that Galois group of the $n$th cyclotomic extension has order $\phi(n)$( $\phi$ is the Euler's phi function.), the writer assumed, without proof, that $n$th cyclotomic polynomial $\Phi_n(x)$ is irreducible over $\mathbb{Q}$.  I know that for n=p, p is prime, $\Phi_n(x)$ is irreducible over $\mathbb{Q}$ by Eisenstein's criterion.  But I don't know how $\Phi_n(x)$ is irreducible over $\mathbb{Q}$ when n is not prime.


Problem: (All info below) I've set up the app to get text from EditText component and add it into a LinkedList once the button is pressed.  Tests: Testing for getText.toString() was successful (so u_in had a usable string) and I also tried to implement a simple array within my MainActivity and perform the same function which worked perfectly. Although I keep getting a NullPointerException with the database class and LinkedList.   I've also tried adding a null check in the OnClick anonymous method, but still got the same error.  Testing using physical device and running Android Studio 2.1  Main class:  public class MainActivity extends AppCompatActivity {  public Data_base db; public String u_in;  @Override protected void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     setContentView(R.layout.activity_main);     check_button(); }   public void check_button() {     Button add_button = (Button) findViewById(R.id.button);     final EditText etext = (EditText) findViewById(R.id.editText);     add_button.setOnClickListener(new View.OnClickListener() {         public void onClick(View v){             u_in = etext.getText().toString();             db.add(u_in,0);             }     }); }   Input class(Initializes information):  public class Input {   public String input;  public int age;      public Input (String input, int age) {         this.input = input;         this.age = age;     }  }   Database class (where I have my linkedlist and methods to manipulate it):  public class Data_base {     public LinkedList<Input> user_in = new LinkedList<>();     public void add(String in, int age) {        user_in.add(new Input(in, age));    }     public LinkedList<Input> getList() {        return user_in;    }  }   Error:   05-02 22:51:59.202 2813-2813/com.example.user.test_app E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.user.test_app, PID: 2813 java.lang.NullPointerException: Attempt to invoke virtual method 'void com.example.user.test_app.Data_base.add(java.lang.String, int)' on a null object reference  at com.example.user.test_app.MainActivity$1.onClick(MainActivity.java:33)  at android.view.View.performClick(View.java:5155)  at android.view.View$PerformClick.run(View.java:20747)  at android.os.Handler.handleCallback(Handler.java:739)  at android.os.Handler.dispatchMessage(Handler.java:95)  at android.os.Looper.loop(Looper.java:145)  at android.app.ActivityThread.main(ActivityThread.java:5832)  at java.lang.reflect.Method.invoke(Native Method)  at java.lang.reflect.Method.invoke(Method.java:372)  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


What is the philosophy behind the prioritization of repositories when Ubuntu tries to install or update an app?  As I learned from , when we have the highest version in the repository, the order of repositories in sources.list file determines the priority. But in the case that repositories have been added to sources.list.d, which principle will be used fir prioritization?   Also in the case that I want to know the priority using command, I learned from  that I can use apt-cache policy.

Which repository will Ubuntu choose to download a package from if the same package is available in more than one repos? Suppose a package A was initially installed from repository X and later I added repo Y which also has package A. Which repo will be chosen to update the package? Also if I completely remove this package and try to reinstall then which repo would be preferred by Ubuntu to install the package?


You can set Ctrl + Shift + 1 to switch keyboard to English, and set Ctrl + Shift + 2 to switch keyboard to some other language. This can be done in Windows settings ("").  Now, my keyboard has a number of additional keys, which are free to bind to user's actions. Keyboard software allows you to specify an application (command line) to execute when such additional key is pressed.  So, I want to assign keyboard switching to these additional keyboard keys. Is there a way to do this via command line or powershell?  P.S. I could write an app to switch keyboard, but I would rather prefer to use build-in features only.

Is is possible to change the keyboard layout via command line on Windows XP/7?


The issue I'm running into is when I try to enter the CLI using CTRL+ALT+F1 or CTRL+ALT+F3, I get the log-in screen and am prmopted for my username.  After entering my username the cursor hops to the next line, the text I enter is displayed on the screen, then it tells me that I entered the wrong password.  If I don't enter anything, the cursor hops to the next line, and after a few seconds it tells me wrong password.    The other detail is that the loop happens about 3 or 4 times until I am prompted for my password again.  I looked through the forum and couldn't find a problem.    I checked my .bashrc but the only thing that is different is I have some GCP stuff there. I commented out all the new lines in my bashrc file that were new and this still happens.    This is using Ubuntu 16.04

I upgraded from 16.04 to 18.04. When I press Ctrl+Alt+F3 I get the terminal which prompts for the username. When I type my username and press Enter, it doesn't wait for my password (its as if I pressed Enter without entering anything). Even if I enter something, the text shown in plaintext and then it keeps on saying my password is wrong. After few times, the screen is cleared and it prompts for my username again and the same loop goes on.


Is there a software to generate the ? $\hskip1.7in$ Specially including "general triangles $(p, q, r)$"...

I'm a computer programmer, and while I like math, this is an area where my understanding of math falls short of what I need in order to apply it successfully.  I've been looking at M.C. , which use a Poincare disk model to illustrate tilings of the hyperbolic plane. What I want to do is generate the coordinates (in the Cartesian plane, for a graphics display) of vertices in such a tiling. But I'm not even sure where to start. It seems like I need two things:   a way to generate the coordinates in the hyperbolic plane, for each vertex of several cells (polygons) in such a tiling; and the formula to convert those coordinates to the Cartesian plane, using the Poincare Disk model.    For example, in Circle Limit I, each fish seems equivalent to a quadrilateral (four other fish touch its edges), and each vertex is surrounded by either 4 or 6 fish. I don't need to generate fish, just quadrilaterals. But I don't know how to do it.  Do you know of software to do this? Or can someone help me with an algorithm?  I want to generate a finite area of the plane (of course?). If an algorithm could help me generate $k$ rings of cells around the origin, that would be most convenient.  Thanks for any suggestions.  P.S. I'd also be interested in hyperbolic tilings besides Escher's, e.g.   P.P.S. I just found some  for drawing hyperbolic tilings (see bottom of the page), which includes generating locations of vertices. I can extract these vertex coordinates by putting in print statements. But they're grouped by line segment rather than by cell, and converting from the former to the latter does not seem easy.


I am trying to spawn a baby villager using the following command: /summon villager ~ ~ ~ {Age:-2000000000}  But it isn’t working. What is my error?

This question was recently split into different questions for each workaround. See   meta posts for more information.   Can you use NBT tags in commands? I’ve tried commands that normally work in Java Edition like: give @s minecraft:planks 30 1 {display:{Lore:["Wooden planks"]}} give @s stone_pickaxe{Unbreakable:1b} give @s item_frame{EntityTag:{Invisible:1b}} summon villager ~ ~ ~ {Offers:{Recipes:[{buy:{id:"emerald",Count:5b},sell:{id:"diamond_sword"}}]}} summon tnt ~ ~ ~ {Fuse:20s}


Let $\{x_n\}$ be a sequence in a Hilbert space $H$. If $\sum_n \|x\|< \infty$, how to show that $\sum x_n$ is convergent in $H$?  There is no doubt that $x_n \rightarrow 0$ as $n \rightarrow \infty$ (right?) since we have that \begin{align*} \sum_n \|x\|< \infty &\iff \|x_n\|\rightarrow 0 \text{ as } n \rightarrow \infty \\ &\iff \langle x_n,x_n\rangle \rightarrow 0 \text{ as } n \rightarrow \infty \\ &\iff x_n \rightarrow 0 \text{ as } n\rightarrow \infty \end{align*}  (it is a property of the inner product that $\langle x,x\rangle=0 \implies x=0$)  What to do next? Can I use the completeness of $H$ somehow?

Does someone know if the following is true:  Let $\mathbb{X}$ be some arbitrary Banach space. $\{x_k \}_{k=1}^{\infty} \in \mathbb{X}$ is a sequence chosen from $\mathbb{X}$.  Now, if the series  $$\sum_{k=1}^\infty \|x_k\|_X$$ converges, would the "more generic" series $$\sum_{k=1}^\infty x_k$$  also converge?  If yes, could you please give the proof (or just mark the proof steps) ?  Thank you.


Currently there is no comment button or @ autocompletion when writing a comment in reply to another comment on Stack Exchange for mobile Chrome  on Android. It would be a good time saver to have this feature.

I use Stack Exchange site through my phone (iPhone) way more frequently than I do through the desktop website. When I do that, I really wish that typing the @ symbol would offer the same auto-completion of names that it triggers on the desktop site.  Is anyone working on getting that feature working? If not, I'd like to ask that you prioritize it.


I want to look at a list of my new posts, not just for the current community I'm logged into, but for all communities together.  How can I do this?

I am able to visit any Stack Exchange site and view all my posts to such site. However, I would like to be able to view all of my posts to all Stack Exchange sites in reverse chronological order, all on one page, and not just per-site posts. Is there a way to achieve this via the user interface?


I am learning regession, and I dont understand why do we need to square in residual sum of squares. whats wrong with just use residual sum to represent as the error value? What is the benefit of squaring the residual?

Why are we using the squared residuals instead of the absolute residuals in OLS estimation?  My idea was that we use the square of the error values, so that residuals below the fitted line (which are then negative), would still have to be able to be added up to the positive errors. Otherwise, we could have an error of 0 simply because a huge positive error could cancel with a huge negative error.  So why do we square it, instead of just taking the absolute value? Is that because of the extra penalty for higher errors (instead of 2 being 2 times the error of 1, it is 4 times the error of 1 when we square it).


Let $V$ be an inner product space and $T:V\rightarrow V$ be a projection on some subspace of $V$.  Let's assume [$\forall x\in V, \|T(x)\|≦\|x\|$] Assuming this, I have proved that $\ker(T)=\operatorname{ran}(T)^\perp$.  However, I don't know whether $\operatorname{ran}(T)=\ker(T)^\perp$. Is it true? Then how do i prove this?

How to prove that if $V$ is a finite dimensional inner product space and $W$ a subspace of $V$, if $P$ is projection map ($P^2=P$) having $W$ as its range and is such that $\|Px\| \leq \|x\|$ for all $x \in V$, then $P$ is orthogonal projection of $V$ onto $W$.


I created an extension for Firefox and named it "Tabs Tree". The extension is for managing browser tabs and representing them in the form of a tree structure. But now I think that I should have named it "Tab Tree" (without "-s"). Like "apple tree" or "orange tree". But I used google and found usages of "Elements Tree" () and "Nodes Tree" () expressions. But also usage of "Element Tree" and "Node Tree".  Are both variants correct to use with that meaning? Or those people who used "Elements Tree" and "Nodes Tree" were wrong? And can I leave "Tabs Tree" as it is as it would be troublesome to change the name now?

My friend said to me one day: "We have a mice problem at UNI". Is "a mice problem" grammatical as opposed to "a mouse problem"?


I have this code:  echo ( $arr['process_refunds'] == 'storecredit' ) ? 'true' : 'false'   The value in $arr['process_refunds'] is 0 type int(0).  It tried in php -a and it turns out that if we compare any string with  == with int(0) it evaluates to true.   Why is that?

What is the difference between == and ===?  How exactly does the loosely == comparison work? How exactly does the strict === comparison work?  What would be some useful examples?


I wanted to know what the sys.platform does in python and what it is useful for. What type of projects would i want to use it for?

What are the possible return values from the following command?  import sys print sys.platform   I know there is a lot of possibilities, so I'm mainly interested in the "main" ones (Windows, Linux, Mac OS)


How does one go about getting the command line prompt back after using the systemctl status command? The command appears to succeed as it displays the status information of the requested service. However, the terminal appears to lock up after using the command.

I use autocomplete a lot in the terminal, like for example for cp command. But sometimes, when I am putting in the directory for the cp command and I press Tab, the list of files is so long that Ubuntu spits out part of the list and then waits for key input before sequentially listing the rest of the files, one by one. This feature is near useless because you never know how many files are left, and almost always end up with an error.   Is there some way to leave this list and go back to my cp command, or do I have to press Ctrl+C and start typing in my cp command again?


I've been having some issues lately with my custom written general purpose vector code, which relies on templates for functionality. I am reluctant to include the implementation in the header file (as is common with templates), as this would add significantly to the compilation time. So I have instead manually instantiated the desired class in the .cpp file. However, this still results in an undefined reference error. I have reduced the code to the following snippet, which still generates an error: matrixd.cpp #include "matrixd.h"  namespace math {     template class _vec2<float>;     template<class T> _vec2<T>::_vec2() {} }  matrixd.h #pragma once namespace math {      template <class T>     class _vec2     {     public:         T x, y;         _vec2<T>();         void reset();     };      typedef _vec2<float> vec2; }  test.cpp #include "matrixd.h"  int main() {     math::_vec2<float> v; }  Error message:  In function main': source.cpp:(.text+0x10): undefined reference to math::_vec2::_vec2()' collect2: error: ld returned 1 exit status  Any help would be appreciated! :)

Quote from :     The only portable way of using templates at the moment is to implement them in header files by using inline functions.   Why is this?  (Clarification: header files are not the only portable solution. But they are the most convenient portable solution.)


At the end of episode 3, Senator Bail Organa brings a baby girl back to his home planet Alderaan. He and his wife, Breha, adopt the girl and raise her in the royal family. He even kept the baby's birth name, Leia.                                  , but I want to know what the royal family told everyone else.  Since royal families are publicly known, how did the royal family explain to the public where the baby came from? If Bail Organa said the child was adopted, wouldn't people be curious about the child's origins? If he said the child was related to the royal family, wouldn't people be able to figure out that was false since they would (probably) know all the members of the royal family? Did he say the child was his by another woman? (Eddard Stark got around the questions by saying "Jon Snow is my bastard child." I can imagine Bail Organa saying something similar.)  If I was a Sith Lord and emperor, and one of the senators just announced a new adoption, and I knew that senator was friendly with a pregnant senator who just died under mysterious circumstances, I would send people to investigate the origins of baby Leia Organa.

I know that Leia is a princess because she was adopted by the Queen of Alderaan, but why would Obi-Wan allow this? Wasn't the original plan of Obi-Wan and Yoda to hide the Skywalkers from Palpatine? Luke was placed into a very low-profile position, being the child of two farmers on a backwater planet. However, Leia occupies a very important political position.  Is there any reason why Obi-Wan would do this if he was trying to hide her?


In my collection is a Magic card printed in a language other than English. How can I determine which card this is?

I bought a bulk pack of magic cards today and one of them was in a foreign language. I don’t know which language it is. Google translate is not recognizing it, even when I take a picture of it. How can I determine what the card says?


Can anyone please tell me whether I should use singular or plural nouns after irrespective of any in the following context? I have searched the Internet and found that both singular and plural nouns are used though plural nouns were more in number.   Here is the context:  Terrorism is a menace. We must come together to end it. Irrespective of any compromise(s) the world should take action against those fringe elements.  I have asked this because I come from a non-native english speaking country where it is said by teachers "any" is always singular. And one more questions if I always use "any" with plural nouns with contexts like the one I cited above, will that be always grammatical? I know "any" can be used with singular nouns in a sentence like "Any man can do it." My question is different. I want to know if "any" with plural nouns is always grammatical in contexts like the one In my example. Could anyone who has good knowledge in the language please answer this?

I always thought with "any" I should use the plural, but on the internet I can find both:   It can be found in any book. It can be found in any books Do you have any books? It can be said in any language.  This can be understood by anyone.  It has been used in any form.   So, what's correct?  Is there any rule?


The Elder Wand in the Harry Potter series was considered to be the most powerful wand, does that make it indestructible? How did Harry just snap the Elder Wand as if it was a thin wooden stick?

So I have seen questions that ask  or   What I am wondering is, according to the history of the  is it actually possible to break the Elder Wand?  Or to ask that question another way, since the Elder Wand is so drawn to strength and power:     However, the Elder Wand knows no loyalty except to strength. So it’s completely unsentimental. It will only go where the power is. (JKR, )   Is there evidence that the Elder Wand would act in self defense to prevent someone from breaking it so it could continue to seek out strength?


I found the  for recording a land departure. "A departure will be recorded if you depart via land and re-enter the United States prior to the expiration date stamped in your passport." I wonder how the land departure could be recorded when re-entering the United States. Does it require some evidence? Please let me know it if there is any person who experienced this.

Seeing as the US does not perform border control on exit (save for occasional spot checks, usually when traffic is moving slowly at the border), how do I make sure my exit by land is recorded so that I'm not incorrectly flagged as an overstayer?  When exiting the US by air or sea, this is not a problem, as airlines and shipping companies send passenger records to US authorities. What about exiting by land though?


I plugged in my USB flash drive into a port that sticks out of the front of the computer and put my files onto it. I didn't immediately take it out, but instead left it in there while I continued using the computer. When I went to stand up, though, my knee bumped against the underside of the flash drive causing to jerk upward and I'm pretty sure damage it (the metal connector bit bends at a slightly more upward angle now than the plastic part).  I thought maybe it would be fine still, but when I plug it into a computer the computer still detects it is there and will install the driver software but won't allow me to access the removable storage. On Windows XP it will show up like normal in "My Computer," but double-clicking to open it results in the pop-up message "Please insert a disc into drive X." On Windows 7 it will recognize that the flash drive was inserted, but it won't show up in Windows Explorer. It does come up in the Device Manager, though.  So since the computer still recognizes that the device is there is it possible to retrieve the data off the flash drive somehow?    P.S. this is not a repost of , and I also have pretty much no experience with soldering so I would like to avoid that option.

A guy I work with just came by to ask me about a damaged thumb drive/USB flash drive.  Apparently his son dropped it on a hard surface and it won't power up anymore.  They've tried plugging it into multiple machines without success, even though each port they tried was able to power other USB devices.  He knows it's not a lost cause because a local tech store is offering to recover the data for $500, but he says they're not worth that much.  I figured someone on SU would have an idea about this; he doesn't care about using the drive in the future, just wants to salvage a few files that would be a pain to recreate.  Is this possible without advanced equipment, and if so, how?  He said he already tried the advice on the Internet about typing in different drive letters and such, but that failed because there was no power going to the drive.  He also said that he opened the case up at one point, but I'm not sure what, if anything, he did inside.


I know that $\text{SL}(N,\mathbb{C}),\text{SU}(N)$ and $\text{U}(N)$ are path-connected. You can use the $\text{QR}$-decomposition for example to see the $\text{SL}(N,\mathbb{C})$-case.  With that knowledge, how can I see that $\text{GL}(N,\mathbb{C})$ is path-connected?  Consider a $\text{GL}(N,\mathbb{C})\ni A=QR$ with $Q\in\text{U}(N)$ and $R$ upper triangular with $R_{ii}>0$.  Is there a path from $A$ to a matrix lying in the already proven cases?

Well, I am not getting any hint how to show $GL_n(\mathbb{C})$ is path connected. So far I have thought that let $A$ be any invertible complex matrix and $I$ be the idenity matrix, I was trying to show a path from $A$ to $I$ then define $f(t)=At+(1-t)I$  for $t\in[0,1]$ which is possible continous except where the $\operatorname{det}{f(t)}=0$ i.e. which has $n$ roots and I can choose a path in $\mathbb{C}\setminus\{t_1,\dots,t_n\}$ where $t_1,\dots,t_n$ are roots of $\operatorname{det}{f(t)}=0$, is my thinking was correct? Could anyone tell me the solution?


Show that the following group is identity:   $$G=\langle x,y,z  \mid xyx^{-1}=y^{2}\, , \, yzy^{-1}=z^{2}\, , \, zxz^{-1}=x^{2} \rangle.$$  This group is its own derived group. So all I get is group is perfect. Am I correct? What else I missed? Should I use tietze transformation, I am not getting anywhere with them.

Problem: Show that the group given by the presentation $$\langle x,y,z  \mid xyx^{-1}y^{-2}\, , \, yzy^{-1}z^{-2}\, , \, zxz^{-1}x^{-2} \rangle $$ is equivalent to the trivial group.   I have tried all sorts of manners to try to show that the relations given by the presentation above imply that $x=y=z=e$. However, I am stuck and would appreciate any hints as to how I should move forward.


Why is the average for $n$ numbers given by $(a+b+c+\cdots)/n$? I deduced the formula for the average of 2 numbers which was easy because its also the mid point, but I couldn't do it for more than 2 numbers.

I've been using the formula for the arithmetic mean all my life, but I'm not sure why it works.  My current intuition is this one:  The arithmetic mean is a number that when multiplied by the number of elements, gives you the sum of all the elements. Because of this fact, it can't be more than the maximum nor less than the minimum, and it should be located somewhat around the center.  But I was wondering if there are other intuitions out there? Why does this formula work? If in passing you could talk about the weighted average as well, that would be nice too.  Thanks


This question may be insanely simple, but I'm unsure. Let's say we have the following function: $$ f(x) = \begin{cases} x & 0 \leq x < 1 \\ x-1 & 1 \leq x < 2 \\ 0 & \text{otherwise} \end{cases}$$ The CDF is obviously $$ F(x) = \begin{cases} \frac{1}{2}x^2 & 0 \leq x < 1 \\ \frac{1}{2}x^2-x+1 & 1 \leq x < 2 \\ 0 & \text{otherwise} \end{cases} $$ How would I calculate the Inverse CDF from this? (Note: The +1 is required to make it add to 1 and not suddenly become negative. I don't know if that matters for the Inverse CDF.)

The p.d.f. of the random variable $X$ is given by $f(x) =  \begin{cases}   e^{x-2} & \mbox{for $0 \leq x \leq 2$}, \\  e^{-x} & \mbox{for $x > 2$}, \\  0 & \mbox{otherwise,}  \end{cases}$ I need to find $F^{-1}(y)$ to construct a generator for $X$. So I start with calculating the cdf by taking the integral of $f(x)$: $$ F(X)= \begin{cases} \frac{e^x-1}{e^2} & 0 \leq x \leq 2 \\ -e^{-x}+e^{-2} & x \geq 2 \\ 0 & o.w \end{cases} $$ Next, I need to find the inverse of this function: $$y = \frac{e^x-1}{e^2} \implies x= \ln(e^2y+1) \text{ for } y \in [0, 1-e^{-2}]$$ $$y=-e^{-x}+e^{-2} \implies x = -\ln(e^{-2}-y) \text{ for }y \in (0, e^{-2})$$ Now at this point I am confused since the intervals for $F^{-1}(y)$ overlap. How do I break this up into cases? Did I screw up a calculation along the way( I retraced my steps and it seems fine...)?


How can I split a string such as "102:330:3133:76531:451:000:12:44412 by the ":" character, and put all of the numbers into an int array (number sequence will always be 8 elements long)? Preferably without using an external library such as boost.  Also, I'm wondering how I can remove unneeded characters from the string before it's processed such as "$" and "#"?

I'm trying to iterate over the words of a string.  The string can be assumed to be composed of words separated by whitespace.  Note that I'm not interested in C string functions or that kind of character manipulation/access. Also, please give precedence to elegance over efficiency in your answer.  The best solution I have right now is:  #include <iostream> #include <sstream> #include <string>  using namespace std;  int main() {     string s = "Somewhere down the road";     istringstream iss(s);      do     {         string subs;         iss >> subs;         cout << "Substring: " << subs << endl;     } while (iss); }   Is there a more elegant way to do this?


Will the desktop be consuming resources if Im not using it?  If so, how do I turn it on/off?

Trying to run a Ubuntu server for the first time... But everything is in a terminal. Is there a way to switch to a GUI?


I have to find the uniformly most powerful size $\alpha$ test for the following pdf- $$f(x|\theta) = exp\{-(x-\theta)\}$$ $x>\theta$  The pdf is 0 for $x\leq\theta$ , Null hypothesis is $\theta = \theta_0$ and alternate is $\theta =\theta_1$.  I am given an i.i.d. sample from the above pdf. I was trying to apply the Neyman pearson lemma but the relative likelihood is constant so I don’t know how to find the UMP size $\alpha$ test, can someone please provide the solution.

For the pdf $f_{\theta}(x)=e^{-(x-\theta)} , x \ge \theta$, find a most powerful test of size $\alpha$, using Neyman Pearson Lemma to test $\theta=\theta_{0}$ against $\theta=\theta_1(> \theta_0)$, based on a sample of size $n$.  I am facing difficulty as the parameter here is range dependent  However, if $X_{(1)}>\theta_1$, then $f_1(x)>\lambda f_0(x)$ if $e^{n(\theta_1- \theta_0)}> \lambda$ would mean rejection of null hypothesis. But how will I make this test a size $\alpha$ test? The ratio is coming to be constant. Please help!


Why is 11 (eleven) not pronounced onety-one or elebenty-leben, and why is it considered the ghetto way of saying eleven?

In short, why is it not oneteen and twoteen, and we start at thirteen in English?  In another thread, I supposed that despite that fact that people have ten fingers, amounts of items leading up to and including twelve were more common because twelve is more easily divisible evenly by two, three, four, and six. Both English and German (which are related) switch to a -teen (-zehn auf Deutsch) ending after twelve. Based on that thread, so does Norwegian. Could this be the explanation?  Looking at other languages (Arabic, Japanese, even a related romance language of French), this doesn't seem to apply, and you'd think that if something so fundamental as divisibility were the explanation, we'd see a more universal distribution across them.


I'm using Ubuntu 16.04, it's as new as I can get without the PC running slow (old computer lol) and I like Ubuntu, but the only thing that bugs me is where the launcher is, I'd like to move the launcher down to the bottom, kinda like Windows, and again I can only us Ubuntu 16.04 because if I us 18.04 it starts running really really slow. If there's not a way I'll eventually get over it. But I would like to move the Launcher to the bottom, I don't mind it if it's a terminal command(as long as you go step by step) or through something else, it's just annoying and seems like it's faster if I move it to the bottom. Thank you to all who's willing to answer my question.

I can’t get used to the new Unity system. I’d like to move the left Unity panel to the bottom of screen (like Windows 7 – more similar is better).  But I can't find a way. Is it possible?


Or maybe not, when I use iwconfig, instead of wlan0 I get wlx00....etc for my wireless card. Is this normal?

A lot of my scripts stopped working after installing Ubuntu 15.10 and I have trouble remembering this new name as I was used to ethx and wlanx for years. Is there a reason for this change? Do I have to get used to this or can I just rename it and go back to good old eth0?  $ ifconfig  enp0s25   Link encap:Ethernet  HWaddr 77:5a:5e:a6:86:d5         inet addr:192.168.31.239  Bcast:192.168.31.255  Mask:255.255.255.0       inet6 addr: fe80::725a:b6ff:fea6:86d7/64 Scope:Link       UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1       RX packets:4833 errors:1332 dropped:0 overruns:0 frame:666       TX packets:5589 errors:0 dropped:0 overruns:0 carrier:0       collisions:0 txqueuelen:1000        RX bytes:3266446 (3.2 MB)  TX bytes:1046654 (1.0 MB)       Interrupt:20 Memory:d3500000-d3520000


I'm a little confused about which is correct:     I’ve made my mind up.   or     I’ve made up my mind.

I'm learning about phrasal verbs, but I'm not sure if I'll use them correctly. Which one of the following phrasal verb uses correct:  -I don't know how to turn down the volume? -I don't know how to turn the volume down?  I always think that they're same, but lately I feel like there must be a rule how to use them correctly, or perhaps they get different meanings?


Let $A$ be a finitely generated $k$-algebra with no nilpotents. What do I need to show in order to prove it's a finite dimensional vector space over $k$?   For example, is it enough to show that $A$ has only finitely prime ideals and every prime ideal is maximal?

Atiyah Macdonald, Exercise 8.3. Let $k$ be a field and $A$ a finitely generated $k$-algebra. Prove that the following are equivalent:   (1) $A$ is Artinian.   (2) $A$ is a finite $k$-algebra.   I have a question in the proof of (1$\Rightarrow$2): By using the structure theorem, we may assume that $(A,m)$ is an Artin local ring. Then $A/m$ is a finite algebraic extension of $k$ by . Since $A$ is Artinian, $m$ is the nilradical of $A$ and thus $m^n=0$ for some $n$. Thus we have a chain $A \supseteq m \supseteq m^2 \supseteq \cdots \supseteq m^n=0$. Since $A$ is Noetherian, $m$ is finitely generated and hence each $m^i/m^{i+1}$ is a finite dimensional $A/m$-vector space, hence a finite dimensional $k$-vector space.  But now how can I deduce that $A$ is a finite dimensional $k$-vector space?


Preface  I have an annotated text dataset on hate speech. Simply put, the dataset consists of a column called text which includes a piece of text, and a column called label which can be either 0 (non-hateful) or 1 (hateful).  Let's call this dataset Dataset A.   I am using this dataset to train a very simple classifier using Logistic Regression. Code:   dataset_1_df = pd.read_csv(d_1_path, sep='\t')  text = dataset_1_df.text    X = text y = dataset_1_df['label'].astype(int)  X_train, X_test, y_train, y_test = train_test_split(X, y, random_state=42, test_size=0.1)  clf = Pipeline([     ('vect', CountVectorizer(max_features=10000, ngram_range=(1, 2))),     ('tfidf', TfidfTransformer(norm='l2')),     ('clf', LogisticRegression()), ])  clf = clf.fit(X_train, y_train) y_preds = clf.predict(X_test)   This classifier works fine. I can produce a classification report like this:   report = classification_report(y_test, y_preds) print(report)   Which outputs:                 precision    recall  f1-score   support             0       0.87      0.70      0.78       410            1       0.94      0.98      0.96      2069      accuracy                           0.93      2479    macro avg       0.91      0.84      0.87      2479 weighted avg       0.93      0.93      0.93      2479   And I can now make predictions like this:   print(clf.predict(['I hate you'])) print(clf.predict_proba(['I hate you']))   Which outputs:   [1] [[0.0749381 0.9250619]]     My Question  I have another dataset, let's call this Dataset B, independent to Dataset A. Dataset B is also an annotated text dataset on hate speech with the same columns.   What I want to do is to test the model I trained using Dataset A on Dataset B. I.e., I want to produce a classification report on my model's performance on Dataset B. Can I do that? If yes, how?  Clarification: I do not want to retrain my model using Dataset B. I want to see how good its performance is on the new dataset.     Similar Questions  There is  question that looks similar based on the title but does not ask what I'm asking.   There's is also  question which asks how to make predictions. However, I know how to make predictions, what I want to do is to test my trained model on a totally new dataset.

I just trained my first model in Python 3.7/scikitlearn (Linear Regression) (well I copied most of the code but its something ^^).  Now I want to actually Use the model. Specifically its about sons heights incorrelating to their fathers. So I now want to enter a new Father-height and get a predictions for its sons height.  How could something like this look like?  I read about "Pickle" to save a model and use it later, seems awsome but how would I use such a saved model?  If anybody can give me a simple answer or even just a link to atutorial would be great. Below is a piece of "my" code just for some context.  #Spliting the data into test and train data X_train,X_test,y_train,y_test=train_test_split(X,y,test_size=0.2,random_state=0)  #Doing a linear regression lm=LinearRegression() lm.fit(X_train,y_train)  #Predicting the height of Sons y_test=lm.predict(X_test) print(y_test)


I have a simple code to work with getters and setters. I have created a object from book class in another class. But this object doesn't recognize by the class. Why is that? I get this error      An object reference is required for the nonstatic field, method, or property 'member'              class Book {     private int num;      public void setNum(int no)     {         this.num = no;     }           public int getNum()     {         return this.num;     }   }  class Program {     Book bb = new Book();     public static void Main()     {         bb.setNum(10);         Console.WriteLine("Insert value" + bb.getNum);     } }

Consider:  namespace WindowsApplication1 {     public partial class Form1 : Form     {         public Form1()         {             InitializeComponent();         }          private void button1_Click(object sender, EventArgs e)         {             //int[] val = { 0, 0};             int val;             if (textBox1.Text == "")             {                 MessageBox.Show("Input any no");             }             else             {                 val = Convert.ToInt32(textBox1.Text);                 Thread ot1 = new Thread(new ParameterizedThreadStart(SumData));                 ot1.Start(val);             }         }          private static void ReadData(object state)         {             System.Windows.Forms.Application.Run();         }          void setTextboxText(int result)         {             if (this.InvokeRequired)             {                 this.Invoke(new IntDelegate(SetTextboxTextSafe), new object[] { result });             }             else             {                 SetTextboxTextSafe(result);             }         }          void SetTextboxTextSafe(int result)         {             label1.Text = result.ToString();         }          private static void SumData(object state)         {             int result;             //int[] icount = (int[])state;             int icount = (int)state;              for (int i = icount; i > 0; i--)             {                 result += i;                 System.Threading.Thread.Sleep(1000);             }             setTextboxText(result);         }          delegate void IntDelegate(int result);          private void button2_Click(object sender, EventArgs e)         {             Application.Exit();         }     } }   Why is this error occurring?     An object reference is required for the nonstatic field, method, or property 'WindowsApplication1.Form1.setTextboxText(int)


After a recent update, ttf-mscorefonts-installer prompted me to accept its license agreement.     ┌─────────────────┤ Configuring ttf-mscorefonts-installer ├─────────────────┐  │                                                                           │   │ TrueType core fonts for the Web EULA                                          │                                                                               │ END-USER LICENSE AGREEMENT FOR MICROSOFT SOFTWARE                             │                                                                               │ IMPORTANT-READ CAREFULLY: This Microsoft End-User License Agreement           │ ("EULA") is a legal agreement between you (either an individual or a          │ single entity) and Microsoft Corporation for the Microsoft software           │ accompanying this EULA, which includes computer software and may include      │ associated media, printed materials, and "on-line" or electronic              │ documentation ("SOFTWARE PRODUCT" or "SOFTWARE"). By exercising your          │ rights to make and use copies of the SOFTWARE PRODUCT, you agree to be        │ bound by the terms of this EULA. If you do not agree to the terms of          │ this EULA, you may not use the SOFTWARE PRODUCT.                              │                                                                               │                                  <Ok>                                         │                                                                           │   └───────────────────────────────────────────────────────────────────────────┘    Screenshot:   For some reason my terminal will not allow me to accept, or for some reason I am pressing the wrong hotkey...  I've tried every letter on the keyboard and Enter among others...  I'm sure there is a very simple and obvious solution to this.  I've also just tried to remove the package completely however the terminal states that due to the package not being correctly installed, I should reinstall the package before removing it.  Very frustrating!  Essentially, because I cannot successfully install this package, I can't really ever upgrade my system because I always have to end up terminating the terminal with the license agreement (thus the upgrade fails).


How I can make color transparent in Photoshop? For example, I have picture of smoke, and I want to make background color (which is black) transparent. How?

This fire image:    As you can see, it has a black background, which I can't delete (because it would probably destroy the smooth-looking fire effect). I want to place some fire in a photo.  However, I remember it was possible to take such images and do something in photoshop so that when you place them over a photo, the black is gone and the fire is perfectly blended there. But I can't remember what feature or option was it. Any ideas?  Photoshop CS5.


I am stuck on level 35. I need 3 friends to unlock the level, but I have tried sending the request and none have received my request.  How do I unlock the level?

After half a weekend spent on conquering Candy Crush Saga levels, I have finally arrived at level 36. Unfortunately, there seems to be a "barrier" of sorts to start playing this level, with two options:   Ask your Facebook friends for help Buy a ticket for $0.99   While option #2 is extremely cheap, I'm curious what option #1 entails. I am personally extremely annoyed when I get enormous amounts of requests from Facebook applications and I don't want to annoy my friends this way. While I know selecting option #1 sends a request to my Facebook friends, what happens after that?


I imported this in as an FBX and all the objects seem to have this weird grouping. How do I remove it and how did I do this?

In Object Mode I sometimes see these black dotted lines starting at some of my objects and ending in some random spot in the space. What are they, how do I manipulate them, and why?


How would we solve this summation?   $$\sum_{i=1}^{88}{\frac{1}{\cos i°\cdot \cos(i+1)°}}$$  I can't seem to make a start anywhere...

Find the sum of the following :   (i) $$\frac{1}{\cos0^\circ \cos1^\circ}+\frac{1}{\cos1^\circ\cos2^\circ} +\frac{1}{\cos2^\circ \cos3^\circ}+......+\frac{1}{\cos88^\circ \cos89^\circ}$$  I tried :  $$\frac{1}{\cos1^\circ}\left[\frac{\cos(1^\circ-0^\circ)}{\cos0^\circ\cos1^\circ} + \frac{\cos(2^\circ-1^\circ)}{\cos1^\circ\cos2^\circ}+...\right]$$  = $$\frac{1}{\cos1^\circ}\left[\frac{\cos1^\circ\cos0^\circ}{\cos0^\circ\cos1^\circ} - \frac{\sin1^\circ \sin0^\circ}{\sin0^\circ\cos1^\circ} + \frac{\cos2^\circ \cos1^\circ}{\cos1^\circ\cos2^\circ} -\frac{\sin2^\circ \sin1^\circ}{\cos1^\circ\cos2^\circ}...\right]$$  For this, as well, I am not getting any pattern to solve further. Please suggest, thanks.


I read many hypothesis to explain the asymmetry between the quantity of matter and antimatter in the universe, most notably through an asymmetry in initial baryogenesis. This assymetry would explain that now matter is in much higher quantity than matter. Asymmetry that I tried to express as { matter } / { antimatter } $\gg$ 1 or $ {N_B} / {N_\bar{B}} \gg 1$.  What permit to assert, to measure this asymmetry if the spectrum of antimatter stellar objects would be indistinguishable from the spectrum of matter ones?  Is the spectrum of matter and antimatter different?  What permit to assert a galaxy is made of matter and not of antimatter?  If there is no evidence, why so many physicists (Sakharov…) work on an explanation of "scarcity" of antimatter?  My personnal fast analysis point of vue is that we didn't take enough into account the fact that as an observer we aren't in a free position to make a correct measure of matter / antimatter received. We are here in the center of a solar system, a galaxy made essentially of matter. This local huge amount of matter is a natural absorbing filter which will stop most of the antimatter cosmic rays reaching us (the observer).  I would say we are like an observer who would look at the sun through a yellow filter and would conclude that the sun has a spectrum with a black ray on yellow.

As we know that matter-antimatter asymmetry is one of unsolved problems in physics. One possible solution to this problem is given as baryogenesis which produce asymmetry in rate of creation between matter and antimatter particles. But doesn't alternate solution like "different regions of space with different type of particles " holds more ground..  Means in one region matter particle dominates (the region we live ) and another region anti matter particle will dominate. When particle-antiparticle pair created from energy (at that energy is so much high that particle- antiparticle pair could be created from energy according to $E=mc^2$) before they meet and annihilate with each other they also has equal chance of meeting with same type of particle in neighborhood, because after some time of big bang the four force were united and gravity was as powerful as remaining three forces. So now in 50% of all pairs destroyed by annihilation and other 50% clumps together with same type of particle means matter with matter and antimatter with antimatter and then inflationary epoch throw these clumps from each other at very large distance so that they can not meet each other and have chance of annihilation. And we now can not see these regions because of accelerated expansion of universe because of dark energy.   Doesn't this hypothesis is more or at least equally valid with baryogeneis hypothesis.


I want to prove the following implication  $$[0,1]~\text{disconnected}\implies(0,1)~\text{disconnected}.$$  My try: Suppose $[0,1]=U\cup V$ with $U,V$ open, disjoint and nonempty.  Using the subspace topology of $\mathbb{R}$ we also have $U=U'\cap[0,1]$ and $V=V'\cap[0,1]$ where $U',V'$ are open in $\mathbb{R}$.  We have $(0,1)=(0,1)\cap[0,1]=(U'\cap(0,1))\cup(V'\cap(0,1))$. This is a union of open sets since $(0,1)$ is an open interval.  How can I prove that this is also a union of disjoint sets?  Will this $U\cap V=(U'\cap[0,1])\cap(V\cap[0,1])=U'\cap V'\cap[0,1]=\emptyset$ be sufficient for showing the disjoint-requirement?  Also, I do not know how to start for showing that $(0,1)$ is union of nonempty sets.   I would appreciate any help.

The closed unit interval $\mathbb{I}=[0,1]$ is a connected subset of   $\mathbb{R}$.   I am having difficulty understanding the proof in my book, which goes:     Suppose that $A,B$ are open sets forming a disconnection of   $\mathbb{I}$. Thus $A\cap \mathbb{I}$ and $B\cap \mathbb{I}$ are   non-empty bounded disjoint sets whose union is $\mathbb{I}$. Since $A$   and $B$ are open, the sets $A\cap \mathbb{I}$ and $B\cap \mathbb{I}$   cannot consist of only one point. (Why?) For the sake of definiteness,   we suppose that there exist points $a\in A$, $b\in B$ such that   $0<a<b<1$. Applying the supremum property, we let $c=\sup\{x\in  A:x<b\}$ so that $0<c<1$; hence $c\in A\cup B$. If $c\in A$ then $c\ne  b$ and since $A$ is open there is a point $a_1\in A$, $c<a_1$, such   that the interval $[c,a_1]$ is contained in $\{x\in A: x<b\}$ contrary   to the definition of $c$.   Why is $0<c<1$? They define $c=\sup\{x\in A:x<b\}$ so it is the supremum of $A$ which is less than $b$ so doesn't that mean $c$ must be less than $b$ ? Also, why is $c\in A\cup B$ ? Lastly, since $c$ is the supremum of $A$ how is there a point in $A$ such that $c<a_1$ and why is it contrary that it is contained in $\{x\in A: x<b\}$ ?


I am a android developer, I recently installed ubuntu in my another desktop that is 32 bit.  I installed ubuntu 14.04 LTS  When I am going to make a virtual android device through eclipse+android sdk, it's not running. It's saying me to update into 64bit.  Can anyone please give me a solution, how can I run it or update to 64bit from 32bit.  Thanks in Advance.

I've got a 32-bit Ubuntu installation running on 64-bit hardware. Now that , I would like to switch to 64-bit without having to reinstall the OS.  This is one of the :  Shawn installed his system using the 32-bit version of Ubuntu, but his hardware is 64-bit and he wants to switch over. He manually installs the amd64 versions of dpkg and apt, replacing the i386 versions and changing which architecture is used as the default; then he installs the amd64 ubuntu-minimal package; then he installs the amd64 ubuntu-desktop package. Over time the remaining i386 packages are replaced automatically on upgrade.  However, when trying to follow the instructions in there, I cannot find any 64-bit version of dpkg or apt.  Did this user story got implemented in a different way in the final spec, or do I need to do something differently?  In short, how can I switch my 32-bit installation to 64-bit?


I need to emulate extra monitors. For example if my system is dual-monitor, I need to trick Windows to think I have 3 monitors or more (and somehow switch between those virtual monitors to see the image).     IMPORTANT!     Windows must think I have 3 monitors (the monitors must appear in 'Screen Resolution' panel so I can change their 'physical' layout. No hardware products please.   It doesn't have to be perfect/efficient. I need this only temporary.

Is there a way to fake a dual monitor for testing.    I have only one monitor and I have to make an application that is suitable for two monitors.  The second monitor screen should appear as a window on my primary monitor.


I am hoping to use a "{" inside a string interpolation statement but I'm having trouble finding the escape character to do it.  var val = "ERROR_STATE"; var str = $"if(inErrorState){ send 1,\"{val}\" }"   Desired output:  if(inErrorState){send 1,"ERROR_STATE"}   The simple solution is to just not use string interpolation, but I think this way of doing it is easier to read.

How can brackets be escaped in using string.Format? For example: String val = "1,2,3" String.Format(" foo {{0}}", val);  This example doesn't throw an exception, but it outputs the string foo {0}. Is there a way to escape the brackets?


I am a relatively new Linux user who has been running Mint on a 2018 Aero 15x laptop for a few months now. Everything works well enough, but I've had miscellaneous compatibility issues and I have heard that Ubuntu has the best hardware support for newer laptops and I am strongly considering switching over. I also really like the look and customizability of Plasma, so would definitely prefer using it over GNOME, but I have a few questions about the differences between KDE Neon, Kubuntu, and Ubuntu running KDE Plasma. I know what each of them are, but I was curious if Neon and Kubuntu have the same hardware compatibility as Ubuntu/if there is any advantage to running Ubuntu with plasma over either of the options with plasma baked in. Any help would be greatly appreciated!

I am willing to use KDE Plasma 5 Desktop environment.  Should I use Kubuntu or Ubuntu 16.04?   If I would use Kubuntu, which advantages would it offer?


I've made a simple drawing:    The distance between these two points is calculated with a simple formula:    Which gives: 5,38   I need to calculate the green point's coordinates, which is set at 80% distance from the B point towards the A point.  I could make a direction vector between A and B, and then, add (dir * 5.38 * 0.8) to the B point itself, but it gives me strange results.  Is there a simpler (and more efficient!) way to achieve that?

I have a velocity vector where my client is at and where its going, and I have the same vector that comes from the server telling where the client should be. Sometimes its a bit different, so I want to interpolate between my current position to the server correct position.    The black arrow is the client velocity vector, the red arrow is the client velocity  vector on the server and the blue arrow is the one that I want to calculate and interpolate to.  How do I calculate the blue vector? Then, how can I linear interpolate between them?


I checked the software manager updated and upgraded everything on my system and then too no updates.  I tried using update-manager -c -d and I can update to development version. But I want to install the stable LTS one.  I am thinking about upgrading through ISO. But is it as good as upgrading through your update-manager or I can lose some things.  In conclusion, please provide me the solution to upgrade to stable 20.04.

I'm following the , but on launching the upgrade tool I get this response:  Checking for a new ubuntu release No new release found   Am I doing something wrong? Is there a workaround?


Here is an example situation which I would like to achieve using ArrayFormula:  Column A is the data, column B is the calculation.    Here is an implementation without ArrayFormula:    Here is how I tried to convert it so I wouldn't have to expand it by hand whenever there is a form-submission (which unfortunately inserts a new row instead of adding just the data):    But as you can see this gives me a circular dependency error:    Which is not strictly true; while the calculations do depend on each other, they never depend on themselves, so it should be possible to calculate them.  Is there any way to achieve this? Or maybe there is a way to make regular formulas expand automatically?  Note: I am using Google Sheets for this, so I am mainly interested in solutions for that tool.

For  question, I've created a Google Apps Script function, that calculates the cumulative sum of a range.  on Google+ made a comment about a more efficient way of calculating the cumulative sum:  function cumulativeSum(array){   var output = [];   for (i in array){     if(i==0) {       if (array[i].length > 1) throw ("Only single column of data");       output.push([array[i][0]]);     } else {       output.push([output[i-1][0] + array[i][0]]);     }   }   return output; }   My question is: can this be achieved with the usage of formula's?


lately it has been very irritating for me because I almost have a fully functioning site about to be launched. This may not seem like a problem, however my web host is running an old version of PHP so I cannot use MySqli_* or PDO, so I am stuck with the deprecated version (MySql_). A user here on S.O has told me that it is IMPOSSIBLE to prevent sql injection attacks whilst running MySql_.   Question: Is it impossible to secure my website from sql injection whilst using MySql_*?

If user input is inserted without modification into an SQL query, then the application becomes vulnerable to , like in the following example:  $unsafe_variable = $_POST['user_input'];   mysql_query("INSERT INTO `table` (`column`) VALUES ('$unsafe_variable')");   That's because the user can input something like value'); DROP TABLE table;--, and the query becomes:  INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--')   What can be done to prevent this from happening?


I am learning about References and Datatypes in Java and this particular code is still confusing me. I understand that all of the primitive types in Java are value types (byte, short, int, long, float, double, boolean, char), and when you're using a string or an object it's a reference type. When I was taught to declare and initialize a variable, I was told to think of it like creating a box. So if I create a variable "y" and give it a value of "5" it's like I've created a box called "y" that contained the value of 5. My teacher said that if I then try to call y in a method (check out the code below for more detail) the value will remain untouched because it's a primitive datatype so I'm only passing in 5, not the variable that CONTAINS 5. Well I'm confused because if I'm passing in the value of 5, why wouldn't the following method add one onto it.  public class ReferenceAndValueTypes {     public static void main(String[] args) {          int y = 5;         addOneTo(y);          System.out.println(y);      }       static void addOneTo(int number){         number = number + 1;     } }   The output is 5 and that confuses me greatly. The teacher says it's because int is a value type so we're not passing the y variable in, and we're not operating on that variable but rather the value of that variable. However, the value of that variable is 5 and since the method adds one, shouldn't it be 6? Or, is it because y is a value type, the method cannot work with it so it just has to print out the initial value of y which was 5?

I always thought Java uses pass-by-reference. However, I've seen a couple of blog posts (for example, ) that claim that it isn't (the blog post says that Java uses pass-by-value). I don't think I understand the distinction they're making. What is the explanation?


i want to use blender models in . To import blender models to 3.js we have to use blender exporter    so i follow a tutorial and do every step correctly .i have included folder inside addon directory.but when i restart blender i can't see a three.js addon . i'm using blender 2.72 version .    as you can see there is no addon as 3.js

There is this addon that was built called Window Generator 2. It can be . However, when I go to the download link it shows up in a new tab as a bunch of code.  How can I download and use this addon in Blender?


I'm adding some new functionality to an MVC4 site. I have just added a global static class and a global variable to hold a value in which is determined at some point during a users visit to the site and will be used as a condition later on.  The thought then occurred to me that I was unsure of just how global a static value is in this context.   Do I have to specify the global value as a session variable?   Or will each user to the site get access to it in their own session anyway and I don't have to worry about one user setting it to one value and another user having access to this set value.

On an ASP.NET website, are static classes unique to each web request, or are they instantiated whenever needed and GCed whenever the GC decides to disposed of them?  The reason I ask is because I've written some static classes before in C# and the behavior is different than I would have expected. I would have expected static classes to be unique to each request, but it doesn't seem like that is the case.  If they are not unique to each request, is there a way to allow them to be?  UPDATE: The answer driis gave me was exactly what I needed. I was already using a singleton class, however it was using a static instance and therefore was being shared between requests even if the users were different which in this case was a bad thing. Using HttpContext.Current.Items solves my problem perfectly. For anyone who stumbles upon this question in the future, here is my implementation, simplified and shortened so that it easy to understand the pattern:  using System.Collections; using System.Web;  public class GloballyAccessibleClass {     private GloballyAccessibleClass() { }      public static GloballyAccessibleClass Instance     {         get         {             IDictionary items = HttpContext.Current.Items;             if(!items.Contains("TheInstance"))             {                 items["TheInstance"] = new GloballyAccessibleClass();             }             return items["TheInstance"] as GloballyAccessibleClass;         }     } }


I am working on automation, while automating a form with number of drop-down's.  The problem with me is, when run the code in maximize mode of window it gives me an Error:     org.openqa.selenium.NoSuchElementException: Cannot locate element with   text: Computers      Build info: version: '2.44.0', revision: '76d78cf', time: '2014-10-23 20:03:00'   System info: host: 'Rajesh-PC', ip: '192.168.0.120', os.name: 'Windows 7', os.arch: 'amd64', os.version: '6.1', java.version: '1.8.0_31'   Driver info: driver.version: unknown    It touches the drop-down but the value is not being clicked.   But when I run same code in minimized window it execute all code successfully without any error, please go-through code of one drop-drown.    driver.findElement(By.name("industrySector-sector")).click(); Thread.sleep(1000*4);  new Select(driver.findElement(By.name("industrySectorsector"))). selectByVisibleText("Computer Software"); driver.findElement(By.cssSelector("select[name=\"industrySector-sector\"] > option[value=\"Computer Software\"]")).click();   HTML code:    <div id="industrySectorFilter" class="custom-select select-width" name="select-type"> <select class="" name="industrySector-sector">     <option value="0">Industry Sector * </option>     <option data-type="43" data-id="1" value="Accounting - Finance">Accounting - Finance</option>     <option data-type="43" data-id="2" value="Advertising">Advertising</option>     <option data-type="43" data-id="3" value="Agriculture">Agriculture</option>     <option data-type="43" data-id="4" value="Airline - Aviation">Airline - Aviation</option>     <option data-type="43" data-id="5" value="Appliance">Appliance</option>     <option data-type="43" data-id="7" value="Architecture - Building">Architecture - Building</option>     <option data-type="43" data-id="8" value="Art - Photography - Journalism">Art - Photography - Journalism</option> </select> </div>

This site contains many questions that are about finding the right locator expression (XPath, CSS, etc) for an object in WebPage or about troubleshooting problems related in invalid or dynamic locators. For instance: .    How one can find a good locator expression? What tools can generate expressions matching a certain element automatically? How to troubleshoot such issues when element does not match expression?


Let $\theta : \mathbb{Z}_8 \to \mathbb{Z}_4$ be defined by $\theta([i]_8) = [i]_4$ for all $i \in \mathbb{Z}$. You may assume that this is a well-defined ring homomorphism. Find $\mathrm{Ker}(\theta)$ and exhibit the partition of $\mathbb{Z}_8$ into cosets of $\mathrm{Ker}(\theta)$.   Can anyone please explain to me what $\mathrm{Image}(\theta)$ and $\mathrm{Kernel}(\theta)$ are. I have the definition and I understand the mapping but how is it used? Why is it relevant? I don't even know if these are the correct questions to ask.

Question: Let $\theta : \mathbb{Z}_8 → \mathbb{Z}_4$ be defined by $\theta([i]_8) = [i]_4$ for all $i \in \mathbb{Z}$. You may assume that this is a well-defined ring homomorphism.    Find Ker($\theta$) Exhibit the partition of $\mathbb{Z}_8$ into cosets of Ker($\theta$).   My Answer: So I found the Ker($\theta$) as Ker($\theta$) $=\{[0]_8, [4]_8\}$ as $\theta[0]_8=[0]_4$ and $\theta[4]_8=[4]_4=[0]_4$.  But I'm stuck on part 2. I was thinking that I would need to show that the partition of $\mathbb{Z}_8$ are equal to $[0]_4$ or $[4]_4$.   Sorry about how I have typed it, haven't really asked questions on the site before.


I am a little confused with determining the relationship status here:   My 4th Great Grandfather was the brother of Mary Branch. Mary is the Great Grandmother of Thomas Jefferson so the line is this:   William Branch   sibling to Mary Branch         son Elias, Grandson Michael, Great Grandson Walton,  2nd Great Grandson Allen, 3rd Great Granddaughter Jessie, 4th Great Granddaughter, Me.    Mary's line she married Thomas Jefferson Sr, they had:   Thomas Jefferson Jr. son, Peter Jefferson grandson, President Thomas Jefferson Great grandson.    So am I a 4th cousin, 3 times removed to President Jefferson?

How do I figure out if someone is a first cousin, second cousin, cousin once-removed, etc?


In the alter universe where Scorpius goes, Voldemort has taken over the world.    Why then is everybody using his name? Even in the original series,   a. Death Eaters call him the Dark Lord b. They get angry at Harry when he uses the name Voldemort c. Under the assumption that everything up to the battle of Hogwarts remains more or less the same, they must've kept the taboo still working, since Ron and Hermione were still on the run, and (possibly) other members of the OOtP.  The third thing, I admit is just an assumption (a valid one I think), but what about the others?

In Harry Potter and The Cursed Child, everyone is using "Voldemort"'s name freely in present day as he is dead and there is no fear of his available death eaters either.   However when Albus and Scorpius try to humiliate Cedric Diggory in Second task of Tri-wizard tournament and while coming back to the present only Scorpius makes it to the present. Here it is complete Voldemort's rule. Voldemort is alive and so is his fear.   But still how come everyone easily takes or say the name of "Voldemort" without any fear? Like "Voldemort and Valour"? Has Voldemort allowed everyone to take his name?


I have a 6 GB file that I want to move to my flash drive. The only problem is that the limitations of FAT32 prevent me. I would like to avoid NTFS. I also can't use exFAT because I would then have difficulty booting from it. It's already fully compressed, so I can't make it any smaller.  Is there a way to work around this limitation?

I recently purchased a 32GB USB 3 stick that was formatted FAT32.  I plugged it into my computer and attempted to copy a film onto it, the file was over 4GB however and it would not let me copy the file across because of the .  After some googling I found that I could format my USB stick to have an  format which would mean I could put files onto the stick greater than 4GB in size and the drive would work on both my Mac and my PC.  The problem with this solution is that my PS3 cannot detect the USB stick when it is formatted with exFAT.  I would like to know if there is a way I can have my USB stick formatted so it can have files greater than 4 GB and work on my PC, Mac and PS3.


I'm reading the Stein-Shakarchi. In Chapter 3 there is a problem and I need to check my solution:  Show that there is no function $f$, such that is holomorphic, defined on the open unit disk that extends continuously to its border, and is equal to the function $g(z)=\frac{1}{z}$ in the border.   Here is my "solution":  Extend the domain of $f$ in such a way that now is $\mathbb{C}$. Now is $\frac{1}{z}$ if $|z|\geq1$, and is equal to $f(z)$ otherwise. By Morera's theorem every triangle has integral egual to 0 at the border of $\mathbb{D}$, so is holomorphic, in the other hand, f and the new g agrees on a set with accumulation point, so they must be equal. Finally, $g$ is not holomorphic in all $\mathbb{C}$, and $f$ is, so we get a contradiction.  Is something wrong here? Do you have any other solution?

How can one show there is no holomorphic function $f$ on the open unit disc $\mathbb{D}$ such that it extends continuously to $\frac{1}{z}$ on $\partial\mathbb{D}$? I mean $f$ takes value $\frac{1}{z}$ when $|z|=1$ and continuous here.  Thank you.


I have an apex class which looks for the old and new values of contacthistory. I am writing a test class for this, but could not write data to Oldvalue and Newvalue. I also tried updating the field which is tracked in history, but that gives null value when I tried assert statement. Here is my class  for(ContactHistory ct: scope){              if((ct.NewValue =='Test Data' && ct.OldValue =='Old Data')||                 (ct.NewValue == 'New Test Data' && ct.OldValue =='Old Data Listing'){ //do something }}   How do I cover this if condition?  Here is my test class:   Test.startTest();         Contact c = new contact(lastname = 'test', email='email@mail.com');              c.TrackedField__c ='OldData';              c.AccountId = acc.Id;         insert c;            c.TrackedField__c ='Test Data';           update c;          Test.stopTest();  ContactHostory ch =[select contactid, OldValue, NewValue from ContactHistory where ContactId =: c.id and Field ='TrackedField__c' limit1]; //this is returning zero results

I have some code that relies on field history tracking by querying the History for a custom object. This works fine, but it appears that the history records aren't created during the test so none of my tests will pass.


edit: THE ACTUAL ANSWER IS IN THE COMMENT SECTION I've not yet get anything so I'll ask a question here then.. It's hard to explain for me (don't even know what to call this problem) but basically this is what it looks like:  ^The red dash box (which is yellow now since I selected the camera) is not on the middle.  ^This is what it should look like. How to like move that red dash box to the middle? I've been using blender for years but never really find out or knew ways or shortcuts to move the camera view red dash box, it can get annoying too if I render a square image. Sorry if this is probably something that people already asked before, I just don't know what to search for this problem :p

I can't figure out how to get rid of this red dotted line in the middle of the viewport.


I will import a lot of images to my project. Drag and drop is easiest way to do that for me. But if I drag and drop any image to my screen it been importing as background reference by default. How can I change this setting to "drag and drop image as plane that visible to render"? I don't want change visibility setting for each image every time. I want drag, drop and render.

I've made a noob mistake and set up a whole scene with empty image objects.  Is it possible to convert them so they would show in the render? I know I can delete everything and start importing everything from scratch as planes, but that would take too much time to start all over again.


I bought myself a new laptop with 1 TB hard-disk.While installing Ubuntu i made that Windows 10 stays in a 200 GB partition.I thought i could create a partition  for Ubuntu while installing but i couldn't.So now i have 200 GB for Windows and 800GB for Ubuntu. I would like to leave 100 GB for Ubuntu and have 700 GB common storage to access from both storage.So any idea how i can do it? I kinda new to Ubuntu and I would like to have your help? Thanks!**

Previously, I have installed Windows 7 on my 320 GB laptop with three partitions 173, 84 and 63 GB each. The 63 GB partition was where the Windows was installed. The rest were for file containers.  Now I changed my OS to Ubuntu 12.04 LTS. I installed Ubuntu by replacing the entire Windows 7 on the 63 GB partition. The rest of the partitions remain as an NTFS Windows partition and I can still access them both (the 173 and 84 GB partitions).  Now I want to change the two partitions of Windows into an Ubuntu format partitions plus most importantly, I want to extend the 63 GB partition to more than a 100 GB because at the moment I am running out of disk space. Whenever I try to install any application, especially using wine, it always complains for a shortage of disk space.  How do I do the extending activity before I entirely format my laptop again and lose all the important files on my partitions?


@isTest public class ConvertTestClass {      public static testMethod void test1() {          Lead__c ld = new Lead__c ();         ld.First_Name__c = 'Test';         ld.Name    ='first';         ld.Company__c ='Test company';         ld.Status__c = 'Qualified';         insert ld;          Test.StartTest();           PageReference pageRef = Page.RedirectingToLead;          Test.setCurrentPage(pageRef);           ApexPages.StandardController sc = new ApexPages.StandardController(ld);         ConvertTheLead testAccPlan = new ConvertTheLead(sc);         testAccPlan.RedirecttoSite();         testAccPlan.convertbutton();         Test.StopTest();      }      public static testMethod void test2() {          Lead__c ld = new Lead__c ();         ld.First_Name__c = 'Test';         ld.Name    ='first';         ld.Company__c ='Test company';         // Set Status as any valid value other then "Qualified"         ld.Status__c = 'New';          insert ld;          Test.StartTest();           PageReference pageRef = Page.RedirectingToLead;          Test.setCurrentPage(pageRef);         PageReference RedirectingToLead = extension.myUpdate();           ApexPages.StandardController sc = new ApexPages.StandardController(ld);         ConvertTheLead testAccPlan = new ConvertTheLead(sc);         testAccPlan.RedirecttoSite();         testAccPlan.convertbutton();         Test.StopTest();         system.assert(ApexPages.addMessage(), 'There should be an error');     system.assertEquals(null, RedirectingToLead, 'Redirect should be cancelled');      }  }

This is a canonical question and answer developed by the community to help address common questions. If you've been directed here, or your question has been closed as a duplicate, please look through the resources here and use them to shape more specific questions. To browse all canonical questions and answers, including more unit test resources, navigate to the  tag.  This canonical question is intended to address several classes of common questions by providing a quick summary and links to comprehensive resources:   How is code coverage obtained and calculated? How do I increase my coverage?  Why can't I cover these lines? Why isn't the body of my loop or conditional statement covered?


I need to pass string into socket send() function which accepts char * only. So here I am trying to convert it:  void myFunc(std::string str)  //Taking string here const is good idea? I saw it on some examples on web {     char *buf = str.c_str;    //taking buf const is good idea?     std::cout << str; }  int main() {     const std::string str = "hello world";     myFunc(str);     return 0; }   Gives error:   test.cpp:6:18: error: cannot convert ‘std::basic_string<_CharT, _Traits, _Alloc>::c_str<char, std::char_traits<char>, std::allocator<char> >’ from type ‘const char* (std::basic_string<char>::)()const’ to type ‘char*’

How can I convert an std::string to a char* or a const char*?


Accetping axiom of choice gives rise to all sort of paradoxes. What if we assume the contrary?

In textbook it says that every well-orderable set is equipotent to an initial ordinal number. However, of course unwell-orderable cannot equipotent to any ordinal number, but is there any set is unwell-orderable? By axiom of regularity we know that every set is well-founded, so can we conclude that every set is well-orderable? If not, which set is unwell-orderable?


I'm tryed with:  $ echo 'Ciência' | tr 'a-z' 'A-Z' CIêNCIA   But the 'ê' character does not change, obviously because it is accentuated. Then I tried with POSIX classes:  echo "Ciência" | tr '[:lower:]' '[:upper:]' CIêNCIA   But the 'ê' continue in lower case.  Could someone help me?

I'm trying to remove some characters from file(UTF-8). I'm using tr for this purpose:   tr -cs '[[:alpha:][:space:]]' ' ' <testdata.dat    File contains some foreign characters (like "Латвийская" or "àé"). tr doesn't seem to understand them: it treats them as non-alpha and removes too.  I've tried changing some of my locale settings:  LC_CTYPE=C LC_COLLATE=C tr -cs '[[:alpha:][:space:]]' ' ' <testdata.dat LC_CTYPE=ru_RU.UTF-8 LC_COLLATE=C tr -cs '[[:alpha:][:space:]]' ' ' <testdata.dat LC_CTYPE=ru_RU.UTF-8 LC_COLLATE=ru_RU.UTF-8 tr -cs '[[:alpha:][:space:]]' ' ' <testdata.dat   Unfortunately, none of these worked.  How can I make tr understand Unicode?


EDIT: The suggested duplicate question doesn't answer my question in any way, shape, or form.  I'm having trouble setting up my RecyclerView adapter. I get two errors:  09-19 20:01:38.601 22710-22710/com.yitter.android E/RecyclerView: No adapter attached; skipping layout   ... and:  java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setAdapter(android.support.v7.widget.RecyclerView$Adapter)' on a null object reference     at com.yitter.feed.FeedActivity.lambda$retrieveYeets$68(FeedActivity.java:402)     at com.yitter.feed.FeedActivity.access$lambda$3(FeedActivity.java:0)     at com.yitter.feed.FeedActivity$$Lambda$4.done(Unknown Source)     at com.parse.ParseTaskUtils$2$1.run(ParseTaskUtils.java:116)     at android.os.Handler.handleCallback(Handler.java:739)     at android.os.Handler.dispatchMessage(Handler.java:95)     at android.os.Looper.loop(Looper.java:148)     at android.app.ActivityThread.main(ActivityThread.java:5417)     at java.lang.reflect.Method.invoke(Native Method)     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)   FeedActivity:  In my initialise() class (within onCreate()), I set up my RecyclerView and adapter:  RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerView);                 recyclerView.setHasFixedSize(true);                 adapter = new FeedAdapter(FeedActivity.this, retrieveYeets());                 recyclerView.setAdapter(adapter);                 recyclerView.setLayoutManager(new LinearLayoutManager(this));   I pass a List based on a query:  public List<ParseObject> retrieveYeets() {         String groupId = ParseUser.getCurrentUser().getString("groupId");         ParseQuery<ParseObject> query = new ParseQuery<>(ParseConstants.CLASS_YEET);         query.whereContains(ParseConstants.KEY_GROUP_ID, groupId);         query.orderByDescending("lastReplyUpdatedAt");         query.setLimit(1000);         query.findInBackground((yeets, e) -> {              if (mSwipeRefreshLayout.isRefreshing()) {                 mSwipeRefreshLayout.setRefreshing(false);             }              if (e == null) {                  // We found messages!                 mYeets = yeets;                  String[] usernames;                 usernames = new String[mYeets.size()];                 int i = 0;                 for(ParseObject yeet : mYeets) {                     usernames[i] = yeet.getString(ParseConstants.KEY_SENDER_NAME);                     i++;                 }                  // Add data to FeedAdapter                 FeedAdapter adapter = new FeedAdapter(                         FeedActivity.this,                         mYeets);                 recyclerView.setAdapter(adapter);              }         });          return mYeets;     }   Full Code:   FeedAdapter:  I have a feeling the problem is in my adapter, but I can't figure it out. What could be going wrong?  Full Code:     Answer:  I changed this in my MainActivity:  RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerView);                 recyclerView.setLayoutManager(new LinearLayoutManager(this));                 recyclerView.setHasFixedSize(true);                 adapter = new FeedAdapter(FeedActivity.this, retrieveYeets());                 recyclerView.setAdapter(adapter);   and in my retrieveYeets() method, removed the following lines:  // Add data to FeedAdapter                 FeedAdapter adapter = new FeedAdapter(                         FeedActivity.this,                         mYeets);                 recyclerView.setAdapter(adapter);

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


I am using:  command > ~/Desktop/file.txt   My problem is that I need to execute this command multiple times, and each time It will give me different outputs, in this moment each time I run it It erases everything and saves the new output in the file, obviously this doesn't work for me since I need to add the new output along the current output.  I will really appreciate any help.

Assuming i have a line that i want to add to a file without opening an editor.  How could i append this line  alias list='ls -cl --group-directories-first'   to this file  config.fish


In Harry Potter and the Half-Blood Prince: A Very Frosty Christmas, there is a scene where they have the radio on. Celestina is singing this famous song "A Cauldron Full of Hot, Strong Love", which Molly loves but Fleur Delacour hates.  I was wondering if that was recorded, or if Celestina Warbeck is singing live. If it is recorded, is it known how wizards do that, and how they save the recording?

In the movie Harry Potter and the Goblet of Fire, there's a scene where the students are preparing for the Yule Ball.   Professor McGonagall is instructing the boys and girls, while Filch is choosing a vinyl record to place in an enormous turntable phonograph with a horn as big as Hagrid.   This has me wondering if the wizarding world, in general, plays vinyl records. Or, if this was just a Muggle artifact that Hogwarts kept as a novelty.   Are there other instances of witches or wizards using or owning phonographs or record players in either the books or movies? If so, what are they? (Examples help to illustrate if this was a one-off or a trend)


ArrayList described as  public class ArrayList<E> extends AbstractList<E>     implements List<E>, RandomAccess, Cloneable, java.io.Serializable   And most of main methods work with E generic type (get, set, add, addAll etc).  But methods contains, indexOf, lastIndexOf and remove take the Object type as parameter - is this only because of inner use or Object.equals() or anything else?

Why isn't  generic?    Seems like Collection<E> could have boolean remove(E o);   Then, when you accidentally try to remove (for example) Set<String> instead of each individual String from a Collection<String>, it would be a compile time error instead of a debugging problem later.


I download the code file (tex) of articles on . But I can not open it by texmaker. Do you know how to do this? For example,    Go to this   See on the right corner  Choose Download: other formats  Choose Download source   Then how can I open the file I have downloaded?

I have recently been trying to recompile ArXiV papers (in math and physics) based on the source code ArXiV provided (since I would like to use the geometry package to resize the articles for an ebook reader), but I've been having issues with articles with included figures and images. In most articles I've seen, such as , the source code is unusable for my TeX editor (TeXworks), since ArXiV seems to encode the information of the images in a way that's hard to use. Is there any way to get around this and recompile these articles myself, images and all?


My ar is not working. People say you can only use AR mode when you have a gyroscope How do I get that?

When initiating a battle it starts off in AR mode, but then warns me saying my phone's orientation is not detected. I am then forced to turn off AR mode. Has anybody experienced this? If so, what are the solutions?    Per comments, I am unsure this is a permissions issue. I have everything turned on.


Based on the idea that hex can persist across short rests (see )  if I cast hex on a bug and killed it, then took a short rest for an hour, would I have hex up for the day (until I broke concentration) and my two spell slots?

Due to the long duration on Hex, it is clearly intended to function across multiple encounters as described in this .  Due to the extended duration, it seems feasible that a warlock could take a short rest to recover their spell slot and thus go into a future combat with a Hex at the ready and a full assortment of spell slots. Is this correct? RAW do not appear to prohibit this.


I have the following code which doesn't align a) and b) with the top of the image. How can I align them?  ... \begin{enumerate} \item Find the unknown values and in each case, give a reason.     \begin{enumerate} \item \includegraphics[scale=0.6]{images/image1.png}\\ \item \includegraphics[scale=0.6]{images/image2.png}\\   \end{enumerate} \end{enumerate} ...

I asked a  a while ago about vertically aligning enumerate labels to the top of table. Now I am having the same problem, but with images. Since my problem was solved in my previous thread, I tried sticking the image in a single-cell table and aligning that with the tabular's alignment parameter, but it seemed to have no effect.  Can someone explain what is the correct way to align this image and why didn't sticking it in a table work as expected? I am simply trying to align the enumerate label with the top of my image.    \begin{enumerate}[label=(\alph*)]   \item\begin{tabular}[t]{l}\includegraphics[width=10cm]{13a.png}\end{tabular} \end{enumerate}