I just started playing No Man's Sky last night and I've already built a couple warp cells for the hyperdrive fuel. But the problem is one of the main pieces, the Suspension Fluid, to craft this was very expensive.   It cost me over 40,000 units just for one in the trade center. Does this price change over time?    Obviously different materials will sell for different amounts in the trade center, but which materials, and other miscellaneous items that I find, should I sell to make more money? Are there certain items and materials that I shouldn't sell?  I'm aware that you can expand your inventory size on your suit and ship, but I haven't found out how to yet. So my item carrying capacity is limited and would need to make several trips back and forth between planets and out to the trade center to sell.

I just blew almost all my money on a really cool lookin' ship. How do I regain solvency without spending a lot of time fiddling around in my inventory?  At the moment I've found a sequence of steps that'll turn 50 carbon and 100 Plutonium into ~5000 Units (by creating Suspension Fluid and then turning it into Electron Vapor). Are there better recipes or sequences of recipes I should look for? Or should I just drop the whole thing and go mine a particular mineral?


My main question is why more liquid would roll down a ramp faster than less for a viscosity assignment, however I would like to have a full understanding of why heavier objects would roll faster down a hill

All other things being equal, if a heavier object will roll at a higher speed down hill than a lighter one, because it's heavier with more mass, then how is it that dropped objects fall at the same speed regardless of their weight?


I know this question has been asked several times, but yet I failed to find a suitable solution for me. Consider me somewhat new to it. I want to change the directory using a variable 'var' in the script file 'test.sh' instead of using cd /dir/dir1/dir2.  Question: file example: test.sh  #!/bin/bash var=/dir/dir1/dir2 echo "$var"   -> works(displays the value of var) cd var     or     cd $var    -> none works, either stay in the same directory or shows error directory doesn't exsist   The directory I wanted to use:  /home/username/Downloads  /boot/extlinux  I have already checked various forums or solutions, but none provided the result. Please help me here.

I'm trying to write a small script to change the current directory to my project directory:  #!/bin/bash cd /home/tree/projects/java   I saved this file as proj, added execute permission with chmod, and copied it to /usr/bin. When I call it by: proj, it does nothing. What am I doing wrong?


I'm developing an application for iPhone with a screen where the user will track his progress. Something like so, as seen in the Two Dots game:    Currently I plan on creating this using constraints and size classes. But I feel its too much of work for each screen size. I've set a background UIImageView and I place different circles, manually hardcoding the position. The curved path in my case is made of a texture. So I can't plot it using Bezier Curves either.  Is there an easier way to do it? Perhaps using SpriteKit or Cocos2D-x?

I'm working on a simple 2D game. I've finished the mobile phone version.  However, my boss wants the game to works on his RT. I'm doing the "conversion" but my buttons are in the wrong places, because I hard-coded the screen size, like this:   texture = game.Content.Load<Texture2D>("StartScreen");  mainFrame = new Rectangle(0, 0, game.GraphicsDevice.Viewport.Width, game.GraphicsDevice.Viewport.Height);   // button definitions  startbrect = new Rectangle(300, 258, 88, 88);  startbtext = game.Content.Load<Texture2D>("bplay");   In this example, mainframe is fine, but startbrect isn't, because I defined the size to match a Windows phone's screen. How can I handle responsive design when all Windows 8 phones' screens are different? Is there a formula or macro to calculate each time the good size?


For example, if I have a creature card that says      Creatures you control have "{T}: Add one mana of any color to your mana pool."   and I have two of these creatures out, do they stack so I can tap a creature to get two mana?

Two very closely related questions:  If a card has two different "Sacrifice this creature for X" abilities on it, does sacrificing it give both benefits?  Likewise, if a card requires a creature to be sacrificed, but that creature has a "Sacrifice this creature for X" ability, do you get the sacrifice benefit when you sacrifice it for the other requirement?


I have that $G$ is a group and that the inctersection of all subgroups of $G$ different from the identity is also a subgroup different from the identity. Prove that every element of $G$ has a finite order.

Let $G$ be a group such that the intersection of all its subgroups which are different from $\{e\}$, is a subgroup different from $\{e\}$. Prove that every element of  $G$  has finite order.  Assume that $a$ has infinite order in $G$. Then let $y\neq e$ belong to the intersection of all subgroups of $G$ different from $\{e\}$. Then $y=a^n$ and $y$ will also belong to subgroup generted by $a^2$ hence  $y=a^{2m}$ for some integers $m$. This contradicts that $a$ has infinte order.  Is this correct?


How to Dispose managed or unmanaged objects Using Dispose Method?  In my application class is implemented IDisposable interface and gave overridden method Dispose(). But my actual doubt is how to dispose managed or unmanaged code with in the Dispose method.  public override void Dispose() {    // What should i do for my unmanaged objects?     // can i make my object set to 'null'? }

I know from reading  that the "primary" use of the IDisposable interface is to clean up unmanaged resources.  To me, "unmanaged" means things like database connections, sockets, window handles, etc.  But, I've seen code where the Dispose() method is implemented to free managed resources, which seems redundant to me, since the garbage collector should take care of that for you.  For example:  public class MyCollection : IDisposable {     private List<String> _theList = new List<String>();     private Dictionary<String, Point> _theDict = new Dictionary<String, Point>();      // Die, clear it up! (free unmanaged resources)     public void Dispose()     {         _theList.clear();         _theDict.clear();         _theList = null;         _theDict = null;     }   My question is, does this make the garbage collector free memory used by MyCollection any faster than it normally would?  edit:  So far people have posted some good examples of using IDisposable to clean up unmanaged resources such as database connections and bitmaps.  But suppose that _theList in the above code contained a million strings, and you wanted to free that memory now, rather than waiting for the garbage collector.  Would the above code accomplish that?


I'm reading this chapter   from a forecasting book.  The author has explained a linear regression model. Now this linear regression model will definitely have some errors in fit. For these errors, the author has listen certain characteristics, which should be taken into account. He assumes that these errors:   Have mean zero; otherwise the forecasts will be systematically biased. Are not autocorrelated; otherwise the forecasts will be inefficient as there is more information to be exploited in the data. Are unrelated to the predictor variable; otherwise there would be more information that should be included in the systematic part of the model.   The problem is that I'm not able to comprehend these and come up with an example to get a hang of these points. Could somebody point out some examples / situations from daily life so as to understand these points. For example the author wrote in point 2.] ..."there is more information to be exploited  in the data"...   What is this information? How does it come into being? If I don't even know how this information comes into existence, then how will I be able to understand its existence or effects for that matter?  Is  there a simple explanation with example for my question? I have been trying to understand this since quite some time, please help.

What are the usual assumptions for linear regression?   Do they include:   a linear relationship between the independent and dependent variable independent errors normal distribution of errors homoscedasticity   Are there any others?


So from what I understand  makes your forests into creature. So are you're forests then affected by summoning sickness, and therefore you are unable to be tapped for mana the turn you play them? If so is there a reasonable to animate you're opponents land like this to set them back?

Note: this is intended to be a canonical question about summoning sickness.  "Summoning sickness", broadly, is the rule that stops you from attacking or paying {T} costs with a creature that you just played. But how exactly does it work? How does it interact with other rules and effects?  For example, if I'm trying to figure out how a creature is affected:   Does the status matter (tapped/untapped, face down/face up, etc.)? What if it came into play, but I didn't cast it? What if it's a token? What if it was on the battlefield when my turn started, but it wasn't a creature? What if it stops being a creature? What if it's a creature and also another card type? What if it's a double-faced card that just transformed? What if it changes control? What if it's a copy of another creature? Which of the creature's activated abilities can I use? Are any of its other abilities affected? Can I tap the creature to pay a cost that is not a {T} cost?   (These examples are primarily taken from questions about summoning sickness that have already been asked on the site)


Let $M$ and $N$ be two smooth manifolds with dimensions m and n, respectively, with $m>n$. Let $f:M\to N$ a smooth map ($C^\infty$). Show that this map can't be injective.  My try: I was wondering how could I reduce this problem to the tangent space, using the differentiability condition, to work with vector spaces, where I know how to proof this result. But I was unable to do it, so any help will be useful.

Let $f:M\rightarrow N$ an injective differentiable functions between the manifolds M and N. Prove that $\dim M\leq \dim N$.   Can anyone give me a hint to solve this theorem? I tried to relate the injectivity of $f$ with the injectivity of its differential but that is not gonna work.   Thanks!


Would anyone have a user-defined function to put in my .basrc to do this. The following example should explain what I have in mind.  Given the following file system:      Level1   Level2  Level3   / TestA ~ - TestB      \ TestC  - TestB            - TestD - CurrentLocation   Assuming the function is called goto.  goto(TestA): Should cd us to the level1 testA directory goto(TestZ): Should keep us where we are and print something like "not found" goto(TestB): Should bring us to level2 testB as its the closest.   The search should only ever go up and not down into parent directories as this may match multiple files.  Thanks

What is the best way to sort the results of $ find . -name scripts -type d by the occurrences of '/' and then choose the first result?  I want to create a function that would cd down to a common folder in a project. I wanted it to be flexible based on your relative directory.  So if I have 10 projects all with similar folder structure:  ~/project-a/project/folder/structure ~/project-b/project/folder/structure ~/project-c/project/folder/structure   I could:  $ cd ~/project-a $ cdd structure   And be dropped down into ~/project-a/project/folder/structure  Update  I'm unable to sort results in any predictable way, example:  $ find . -type d -name "themes"  ./wp-content/plugins/contact-form-7/includes/js/jquery-ui/themes ./wp-content/plugins/jetpack/modules/infinite-scroll/themes ./wp-content/plugins/smart-youtube/themes ./wp-content/plugins/wptouch-pro/themes ./wp-content/themes ./wp-includes/js/tinymce/themes   I'd like the cdd function to drop down to the closest result. In this example it'd be ./wp-content/themes.


how would I create up to 15-20 random numbers between 100-200 in java?  I have this atm but it creates any random numbers but I want the numbers to be between 100 and 200 but I don't know how I would go about adding this to the code below. please can someone help.  Random rand = new Random();     int Randnum;     for(int i = 0; i <=20; i++) {         System.out.println(Randnum + " ");          }     }

How do I generate a random int value in a specific range? I have tried the following, but those do not work: Attempt 1: randomNum = minimum + (int)(Math.random() * maximum);  Bug: randomNum can be bigger than maximum. Attempt 2: Random rn = new Random(); int n = maximum - minimum + 1; int i = rn.nextInt() % n; randomNum =  minimum + i;  Bug: randomNum can be smaller than minimum.


I'm quite familiar with Principal Component Analysisis, as I use it to study genetic structure. Lately, I was revisiting some of the functions I was using in R (pcoa() from the ape package and prcomp()) and I realized they don't give the same results for the explained variance, and I'm not sure which one to believe.  My distance matrix is already centered and might sometimes contain negative eigenvalues. I'm aware that pcoa() uses eigenvalue decomposition while prcomp() uses single value decomposition, so I expect the results to be slightly different. The scales of the axis that I obtain with each analysis are not the same, but why is the explained variance almost double with prcomp() (in the full dataset)?  I did some digging and apparently pcoa() does a transformation of the distance matrix $M$ of dimensions $m \times m$  $D=O(-0.5M^2)O$   where   $O=I-1/m$   $I$ being an identity matrix of $m \times m$. The rest of the PCoA is performed with this $D$ matrix in a similar fashion as in prcomp() (but using eigenvalue decomposition instead of single value decomposition). Might this be the cause? Part of the transformation centers the data, but why the $-0.5M^2$? I can't seem to find anywhere the reason for this.    Example dataset  With a reduced dataset (image 1) the explained variances for PC1 and PC2 are 0.44 and 0.30 with prcomp(); 0.36 and 0.27 with pcoa(). I understand that a small difference is normal, since both perform slighlty different methods, but with the full dataset (image 2), the PCs are almost identical but divided by 10 yet they explain 0.32 and 0.22 in prcomp() and 0.14 and 0.11 with pcoa()!  Sorry but I can't figure out how to produce a better reduced dataset...  Kdist<-matrix(c(0.06,0.73,0.76,1.28,1.25,1.27,1.38,1.34,1.43,1.35, 0.73,0.01,0.76,1.31,1.31,1.28,1.38,1.35,1.40,1.34, 0.76,0.76,0.06,1.27,1.31,1.29,1.36,1.34,1.39,1.32, 1.28,1.31,1.27,0.17,0.67,0.89,1.36,1.31,1.28,1.31, 1.25,1.31,1.31,0.67,0.00,0.94,1.35,1.32,1.38,1.34, 1.27,1.28,1.29,0.89,0.94,0.07,1.29,1.30,1.24,1.30, 1.38,1.38,1.36,1.36,1.35,1.29,0.11,0.96,0.81,0.87, 1.34,1.35,1.34,1.31,1.32,1.30,0.96,0.09,0.88,0.96, 1.43,1.40,1.39,1.28,1.38,1.24,0.81,0.88,0.13,0.93, 1.35,1.34,1.32,1.31,1.34,1.30,0.87,0.96,0.93,0.15),10,10)  pc<-ape::pcoa(Kdist) prc<-prcomp(Kdist)  vec.prc <- -prc$rotation[ ,1:2] var.prc <- round(prc$sdev^2/sum(prc$sdev^2),2) vec.pcoa <- pc$vectors[ ,1:2] var.pcoa <- round(pc$values$Relative_eig[1:2],2)  par(mfrow=c(1,2)) plot(vec.prc, main="prcomp",pch=19,cex=2,      xlab=var.prc[1], ylab=var.prc[2]) plot(vec.pcoa, main="ape::pcoa",pch=19,cex=2,      xlab=var.pcoa[1], ylab=var.pcoa[2])

How are PCA and classical MDS different? How about MDS versus nonmetric MDS? Is there a time when you would prefer one over the other? How do the interpretations differ?


I have just installed Ubuntu 18 on my Asus ROG I also have windows 10 on my hdd (and also had id before ubuntu). After installing ubuntu I had some problems getting grub to actually show up and let me choose which OS it should boot into.  Now, when I try to boot into windows I get a black screen with a blinking cursor. but fortunately I can still boot into ubuntu.   I could also mount the windows partition and see that is intact, so the OS still is there.   My question is how can I repair the windows bootmanager (i think this is the problem here) from ubuntu. Thank you!  I have also downloaded a windows 10 iso image and wrote it on a usb stick, but when I try to boot from the stick, it just freezes and the asus logo remains stuck on the screen.

I installed Windows on my computer, followed by an installation of Ubuntu. However, now I'm unable to boot into my Windows install.  What can I do to fix this?


I recently downloaded Virtual Box and Ubuntu to do some quant trading and ran into some issues with the installation process of Ubuntu in Virtual Box itself. I googled some solutions but have run into some problems with some of them while some others have worked but Ubuntu is still slow.   1) I enabled 3D acceleration which made it a little faster but still quite slow.   2) I tried to install CompizConfig via Homebrew but it wouldn't install. brew install compizconfig-settings-manager && ccsm is what I tried but I found get a "No formulae found in taps error".   Could someone suggest what is going wrong with this process? How should I make my Ubuntu run faster in my virtual machine? Will assigning more RAM to it help?  Edit- Just to be clear, my Ubuntu's screen goes black due to unresponsiveness during the installation process itself.   Thanks in advance!

I am trying to run an Ubuntu guest on Windows 10 using VirtualBox. I found the Ubuntu guest was running with slow response after the installation. I found some previous solutions for this problem by changing the settings under machine (like activating 3D acceleration, etc.), but I find my settings are locked. What is the solution for this? How to make the options active?


I was reading this note that compares grid search with random search algorithm for hyperparameter tuning:  In the note the author says: "Random search solves the curse of dimensionality, since we often don’t need to increase the number of sample points exponentially as the number of dimensions increases." Is this really true? I am confused because based on my internet search, some sites state that random search incurs less computational cost than the grid search whereas I have seen some other sites that says random search incurs just as much computational cost as grid search. I am confused. Does random search incur less computational cost than the grid search? If so, why is this the case? Thank you,

I know that, for grid search algorithm, the computational cost of the grid search algorithm would be $O(v^p)$ optimizing $p$ parameters each of which can take on $v$ values, then the computational cost of the grid search algorithm would be $O(v^p)$. But I am not sure what is the computational cost for conducting random walk algorithm. Would it be simply $O(p)$? Thank you,


I have 10k in an old pension plan with a company I no longer work for. I have a 401k currently with my present employer and would like to take the 5k and start an stock trading account. Would this be wise?

I know that with a Roth IRA, contributions can be withdrawn penalty-free at any time. If I rollover a Roth 401k into a Roth IRA, can I do the same with the contributions made to the Roth 401k?   I've  that the entire Roth 401k->Roth IRA rollover counts for penalty-free/tax-free early withdrawal, but that sounds too good to be true.


I am supposed to create a log analysis software for my Master Degree thesis.  Currently I am in the data collection phase :) so I need a way to read a file in real time. For example I have to monitor the "/var/log/auth.log" file and to look for failed logins (just an example among the 1000000s to come for my program:) ). So I need to read the file line by line. OK, if I were to use a scripting language (Python, Ruby) this would be really easy, but since I am in JAVA, I wasn't very lucky. Anybody gotta clue how to read a file in Real Time, maybe an example? Thanks in advance.

I'm wondering what techniques and/or library to use to implement the functionality of the linux command "tail -f ".  I'm essentially looking for a drop in add-on/replacement for java.io.FileReader.  Client code could look something like this:  TailFileReader lft = new TailFileReader("application.log"); BufferedReader br = new BufferedReader(lft); String line; try {   while (true) {     line= br.readLine();     // do something interesting with line   } } catch (IOException e) {   // barf }   The missing piece is a reasonable implementation of TailFileReader.  It should be able to read parts of the file that exist before the file is opened as well as the lines that are added.


There is a natural bijection $$ \operatorname{Map}(X\times Y,Z)\cong\operatorname{Map}(X,\operatorname{Map}(Y,Z)),\quad f\mapsto(x\mapsto(f(x,{-})).  $$ If $X$, $Y$, $Z$ are topological spaces one can ask if the 'exponential law' $$ C(X\times Y,Z)\cong C(X,C(Y,Z)) $$ still holds. And for the compact-open topology on $C(-,-)$ it is well-known that if $Y$ is locally compact and Hausdorff (or just strongly locally compact) and $X$ is Hausdorff, then above bijection induces such a homeomorphism.  I'm asking for a counter-example to the exponential law in the case where $Y$ is still (strongly) locally-compact but no separation axioms are assumed.  Comments. AFAICS,   If $Y$ is (strongly) locally-compact the set-theoretical exponential law always induces a bijection between LHS and RHS. This bijection maps open sets of the form $M(K_1\times K_2,U)$ to open sets of the form $M(K_1,M(K_2,U))$ (where $M(K,U)=\{f:f(K)\subset U\}$). If $X$ is Hausdorff the later sets form a subbase of the compact-open topology on RHS.   This explains where Hausdorff condition is used in the proof (in the form it's written e.g. in Hatcher's AT book) — but I'd still would like an explicit counter-example.

I read that in the category of topological space it is not true that $\operatorname{Hom}(X \times Z, Y) \cong \operatorname{Hom}(X, \operatorname{Map}(Z, Y))$ for every $X, Y, Z$ topological spaces. In particular, I read that this does not work when $Z = \mathbb{R} \setminus \{ 1/n \mid n \in \mathbb{N}\}$. This was not explained, i.e. there was no example.   I am looking for an example or – maybe better – just a hint.  EDIT   $\operatorname{Map}(Z, Y)$ is endowed with the compact-open topology $\cong$ means just bijection; i.e. there is already an obvious bijection as sets, but the claim is that (I think) sometimes the "output function" is not continuous


For Oracle licensing topics I need to identify how many sockets and cpus are actually installed on the hardware. On windows this information can be found by the cmd command “systeminfo”.

I wanted to find out how many cores my system has, so I searched the same question in Google. I got some commands such as the lscpu command. When I tried this command, it gave me the following result:  $ lscpu Architecture:          x86_64 CPU op-mode(s):        32-bit, 64-bit Byte Order:            Little Endian CPU(s):                4 On-line CPU(s) list:   0-3 Thread(s) per core:    1 Core(s) per socket:    4 Socket(s):             1 NUMA node(s):          1 Vendor ID:             GenuineIntel CPU family:            6 Model:                 23 Stepping:              10 CPU MHz:               1998.000 BogoMIPS:              5302.48 Virtualization:        VT-x L1d cache:             32K L1i cache:             32K L2 cache:              2048K NUMA node0 CPU(s):     0-3   In particular, this output shows:   CPU(s): 4 Core(s) per socket: 4 CPU family: 6   Which of those indicates cores of a Linux system?  Is there any other command to tell the number of cores, or am I assuming it is completely wrong?


Is there any particular danger (apart from bricking) that may stop you from rooting Samsung Galaxy S3? Anybody has a good tutorial? And if something goes wrong what to do?

I see lots of tutorials telling me how to root my phone (Motorola Droid), but none of them mention any potential "side effects."  Aside from a few relatively minor issues that seem to require rooting to fix, I'm basically happy with the phone and therefore a little leery of messing with a device that cost me a lot of money and is only a few months old.  Assuming that I'm just talking about rooting, and none of the typical post-root actions (like installing a custom ROM), am I taking any risks by choosing to root?   Does it have the potential to brick the device? Will it void my warranty? Will I stop getting updates? Will the cops show up at my front door the next day? (Yes, I'm being facetious.) Anything else I should be aware of?   (See also: )


Given a string which contains a date as a substring, how can I convert that substring from one date-format to another? More specifically, I have the following questions:   How can I convert the date-string "10/24/2017 8:00:00 AM" to the date-string "20171024 8:00:00 AM"? How can I convert "Data1|Data2|Data3|10/24/2017 8:00:00 AM" to "Data1|Data2|Data3|20171024 8:00:00 AM"? If I have a file called "Sample.csv" containing lines of this form (i.e. pipe-delimited data), how can I convert the date in each line of "Sample.csv" (as in the previous question)?

I have a .csv file contains   Data1|Data2|10/24/2017 8:10:00 AM   I want to change date and time format of column 3 as following:  From 10/24/2017 8:10:00 AM (12-Hour) to 20171024 08:10:00(24-hour).  Not using -d


Stack Overflow has a bunch of nice UI things that are XHR'd.  However, when I vote to -1 an answer, I need to reload to get the delete link. It's not very  obvious, as most things just work.  Could we enable the link automatically in this case?

I used to be able to cast the first downvote on an answer with zero-score and then immediately click the delete link under the answer.  Now, I cast the first downvote and then need to refresh the page for the delete link to be visible.  Is there a reason why the delete link isn't added when casting the first downvote? I liked the faster behavior of the old mechanism.


In trial the game was in ENGLISH but by some reason after i have purchased, the game comes "language locked". Why they do this? I've played RPG's in English since my childhood, work with native speakers, played DA:O in English and ... Can`t play the game in English? Why the trial is in English and there are no information about "language lock" on store?  I`ve tried 5 different tutorials to put the game in English, even change the registry HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\BioWare\Dragon Age Inquisition  Locale to en_EN and GDFBinary to GDFBinary_en_EN.dll and nothing works. The translation s***s. The abilities description makes no sense and the use of therms that nobody uses in my home country such as "melindroso" is ridiculous. Looks like a google translation translation of a google translation translation. I wanna play in ENGLISH. I've tried to get a refund since the game is unplayable with this piece of **** translation but the refund """failed""". Thanks for punishing someone who purchased a original copy while people who don't follow the rules and prejudices the game industry can play in any language that they want.  Note that :  1 - The trial was in English 2 - According to ORIGIN store of my region ENGLISH IS A SUPPORTED LANGUAGE    3 - I did not see any advised about language lock 4 - I have tried to enter in contact with origin support. According to the site the waiting time is 5 minutes but in reality... 30 minutes and nobody appears.  EDIT > Is different(not duplicate) because the other questions works for the 2014 game. After the recent updates, the solution isn't working. So i need a solution to 2017 version of the game.    EDIT 2 HOW I managed to put DA:I to English  Since the other solutions works only with older versions, i decided to download old version files then use the another method. Finally works. The unique small problem is that i will be forced to play the tutorial again because

In the answer to , I was advised:      Yes you have to download the language pack. And you also have to go here: C:\Program Files (x86)\Origin Games\Dragon Age Inquisition\Data\Win32        In the folder loctext leave only the files en.sb and en.toc present, put the others in a folder named temp.   In the folder locfacefx make a copy of en.sb_DiP_STAGED and en.toc_DiP_STAGED, rename them to en.sb and en.toc. place the other language files into a temp folder   When I started the game the language was changed also into the interface. Take notes on what you have done and keep the original files in case something doesn't work, but for the moment that seem to work."   I have no en.sb_DiP_STAGED and en.toc_DiP_STAGED files in my Origin version of the game.


I don't even know where to start here. Also, if it is a group homomorphism, I have to determine whether they are injective or surjective. Any help would be great, thanks!

When is mapping $g$ to $g^{-1}$ a group homomorphism? It just means that the map maps the identity to the identity and inverses to inverses. So does that mean it's only a homomorphism if the inverse is itself?


I have a simple request: Is there a way to quickly find out what a particular option for a command means using man? I know you can just Google for it, but I want to use the man pages if possible.  Something like man ls -l which seems identical to be identical to man ls, but I would like to find out what the -l option does, without having to scroll down to it.

Suppose I want to know the usage of -i switch in grep command without scrolling. I need the specification just for that command or at least see the screen show that first. So how? As you can say that in general not just for grep -i.


Woman planning to visit me from Ukraine to the US applied for a visa and such, claims to have paid for the visa but needs 500 dollars more for the airfare from Ukraine to the US. She says strict rules apply that the airfare cannot be purchased by US person, and must be purchased in Ukraine by person applying for the visa because of terrorist issues, etc..   Is there truth to such?

On Travel.SE we often see questions about a person (usually a love interest) asking for money to pay for airfare, visas, permits and other expenses. For example        What general advice can be given in such situations to the person asking the question? Is it all a scam or can there be legitimate situations in which an online friend could be asking for money?


Sometime back I installed Ubuntu on my desktop, not knowing that I was creating problems for the future. Now I want to re-install windows completely instead of Ubuntu, but my computer is not booting from USB or a CD, and I can't use the windows installer since i do not have a partition that is required by the windows installer. What should I do?

I have absolutely no experience with Linux, and I desperately need to get my computer back up and running again with Windows.  How do I remove Ubuntu and reinstall Windows?    Editor's note: many of the answers are about removing Ubuntu from dual-boot but keeping Windows (which is a bit complicated), while other answers are about removing Ubuntu from single-boot (which is easy: basically just format the disk while installing Windows). The question as written is ambiguous between dual-boot or single-boot.


I am building a simple classification model, the classification model is used for identifying negative or positive feedback on a ticketing system. The tickets have alot of categorical data with high cardinality and the data should be of significance in the model. Is there any standard ways of using these categories without creating hugely sparse data.

What techniques are available for collapsing (or pooling) many categories to a few, for the purpose of using them as an input (predictor) in a statistical model?    Consider a variable like  (discipline chosen by an undergraduate student). It is unordered and categorical, but it can potentially have dozens of distinct levels. Let's say I want to use major as a predictor in a regression model.  Using these levels as-is for modeling leads to all sorts of issues because there are just so many. A lot of statistical precision would be thrown away to use them, and the results are hard to interpret. We're rarely interested in specific majors -- we're much more likely to be interested in broad categories (subgroups) of majors. But it isn't always clear how to divide up the levels into such higher-level categories, or even how many higher-level categories to use.  For typical data I would be happy to use factor analysis, matrix factorization, or a discrete latent modeling technique. But majors are mutually exclusive categories, so I'm hesitant to exploit their covariance for anything.  Furthermore I don't care about the major categories on their own. I care about producing higher-level categories that are coherent with respect to my regression outcome. In the binary outcome case, that suggests to me something like linear discriminant analysis (LDA) to generate higher-level categories that maximize discriminative performance. But LDA is a limited technique and that feels like dirty data dredging to me. Moreover any continuous solution will be hard to interpret.  Meanwhile something based on covariances, like multiple correspondence analysis (MCA), seems suspect to me in this case because of the inherent dependence among mutually exclusive dummy variables -- they're better suited for studying multiple categorical variables, rather than multiple categories of the same variable.  edit: to be clear, this is about collapsing categories (not selecting them), and the categories are predictors or independent variables. In hindsight, this problem seems like an appropriate time to "regularize 'em all and let God sort 'em out". Glad to see this question is interesting to so many people!


How to skip page counting on blank pages created automatically by openright option? I have tried two solutions, , but none works for me.  Let's say page 9 is the last page of chapter 1 and page 10 is a blank page. The chapter 2 is starting with page 11 on the right currently which is correct except for the page number which should be 10. I want to modify the page numbers only and not to remove the blank page or change the openright. Hope that it's clear now.

I'm working on a document that's a 300-page (scr)report, originally set up for one-sided printing. I'm currently preparing a second version of it that I want to be printed two-sided, naturally with the parts and chapters opening right. Its contents and layout are (and have to be) identical to the ›source‹ document except for the footer layout.  All this has been hassle-free, except for one thing: the blank pages that are inserted to make sure that parts and chapters start on recto pages only. Natively, TeX will count these pages as it does non-blank ones -- but of course this throws off the correspondence between the two document's page numberings.  compare:  \documentclass[twoside=true,open=right,paper=A5]{scrreprt} \usepackage{blindtext} \begin{document} \Blinddocument \Blinddocument \Blinddocument \end{document}    and  \documentclass[twoside=false,open=any,paper=A5]{scrreprt} \usepackage{blindtext} \begin{document} \Blinddocument \Blinddocument \Blinddocument \end{document}    Is there an elegant way to take those empty pages out of the ›official‹ numbering (i.e. the one that's printed as opposed to TeX internal one)? Maybe by establishing two different sequences of page numbers? I can certainly think of a way to fiddle with the page counter whenever an implicit \cleardoublepage is invoked, but I guess that'll do more harm than good.  I do see the problem: what I want, effectively, is going to question the unambiguous correspondence between recto/verso and odd/even -- which I'm sure TeX would prefer to preserve...


This is the default Drupal menu:

0.0 Bla

0.1 Bla

     1. Bla

1. Bla

2. Bla

3. Bla

           4. Bla

4-1. Bla

4-2. Bla

4-3. Bla

   How to add a span after my menu link  For example

 0.0 Bla

 0.1 Bla

 1. Bla

 1. Bla

 2. Bla

 3. Bla

           4. Bla

 4-1. Bla

 4-2. Bla

 4-3. Bla

How can I add HTML tags into menu title?  I'm also tryed the following code.   function adminimal_theme_preprocess_menu(&$vars) {   if ($vars['menu_name'] === 'main') {     $vars['items']['standard.front_page']['title']='<i class="icon-home"></i>';   } }   It also converts tags into HTML entities.


That's it - I got tired from the constant problems on and about Windows I'm having. Network issues, performance issues, compatibility issues... But I'll seriously miss OneDrive integration (all my files are there). There is some kind of app that can sync with it? And what is the easiest way to install JDK? Through PPAs? Note that I have no plans to keep Windows, I'll just replace the d*mn thing with Ubuntu (maybe Mint).

Since canonical is  Ubuntu One, what are the possible alternatives?  I currently use Ubuntu One as a backup service for my Documents folder and various other folders I deem important. Of course I have backups on an external hard drive as well, but nevertheless, I find Ubuntu One to be very useful. What I'm especially looking for is a cloud service that does not need a special folder (such as a dropbox or google drive folder); something that is able to integrate into my own file system and syncs just any folder I want to.   I am aware that this question is rather subjective, but I do guess many people who have used Ubuntu One are now in the dark.


I want to cref to a figure but somehow it  gives the chapter the figure is in instead of the figure number. The code I used is written down below:  From which it follows that the vector $\mathbf{\psi}$ has only two independent components as shown in \cref{eq:hhd.13} In \cref{fig:hhd.1} a wave propagating in the x-z plane shown, with a in-plane shearwave SV and an anti-plane shearwave SH.  \begin{equation}\label{eq:hhd.13}  \frac{\delta \psi_y}{\delta y}=-\left(\frac{\delta \psi_x}{\delta x}+\frac{\delta \psi_z}{\delta z}\right)  \end{equation}  \begin{figure}\label{fig:hhd.1}  \includegraphics[scale=3]{./Figures/PSV-SHwaves.jpg}  \caption{P-wave, vertical S-wave (SV) and horizontal S-wave (SH)}  \end{figure}   At the place where I refer to figure 5.1. (as the caption of the figure) describes, latex prints chapter 5.

\documentclass{article} \usepackage{algorithm}  \begin{document} \setcounter{section}{54} \section{A section with no label} \begin{algorithm} \label{myalg} \caption{An algorithm with the label `myalg'.} \end{algorithm} Reference to myalg: \ref{myalg}. \end{document}   With this code, the reference givens 55 (the section number); if I move the label after the caption command, I get the correct reference (1).  Why should this be the case? I find it confusing: when thinking about an algorithm as an environment, you expect to be able to label it right after you began it. At the very least I would expect some kind of error or "??" to appear, rather than the previous environment or reference-able entity being used.


I'm attempting to put this into a VF page which will be the New page for an object. The code is supposed to run this query based upon the value of a field, but I'm getting this error when trying to create a New record :   List has no rows for assignment to SObject   I'm guessing it's because there is not yet a value in the field which is being used to query upon? But that's just my (semi) educated guess. I tried putting those IF ELSE statements in it :   public with sharing class MyController5 {      public account acc {get;set;}     public string names {get;set;}     public Contract_Overview__c contract {get;set;}     string contractid;      public MyController5(apexpages.standardcontroller controller){         acc = new account();         contractid = system.currentpagereference().getparameters().get('id');         contract=[select account__c,Subsidiaries_On_Contract__c from Contract_Overview__c  where id =:contractid];     }      public list<selectoption> getitems(){         List<selectoption> options= new list<selectoption>();         account a =[select name , (select name from Subsidiaries_and_Brands__r) from account where id =:contract.account__c];          if (account.isEmpty(){             name == ‘No Sub Selected Yet’;         } else {           For(SubsidiariesAndBrands__c s : a.Subsidiaries_and_Brands__r){             options.add(new SelectOption(s.name,s.name));         }         return options;     }      public void execute(){}      public void save(){         contract.Subsidiaries_On_Contract__c=names;         update contract;     }  } }   but that's giving me this error when I try to save the code :   Error: Compile Error: line 18:14 no viable alternative at character '‘' at line 18 column 14   Line 18 is this one :   name == ‘No Sub Selected Yet’;   I guess I'm referring to the wrong variable, or just not assigning it the correct alternative ? Does anybody have an idea on this ?   Thank you very much for any help.

I am getting "Error System.QueryException: List has no rows for assignment to SObject".   Line 1: Account ac = [select id from Account where name='testaccount' limit 1] Line 2: if(ac != null) {           //do something         }   I got the above error in line 2 if there is no record.   Any help?


I just got back my Java test paper and there is one question that has been bugging me.  There was a question:  What is the output of the following program?  public class Swap {     public static void swap(int[] a){         int temp = a[1];         a[1] = a[0];         a[0] = temp;     }      public static void main(String[] args){         int[] x = {5,3};         swap(x);         System.out.println("x[0]:" + x[0] + " x[1]:" + x[1]);     } }   The thought that first came to my mind was that this was a trick question. Since the swap method return type was void, I thought that it had no effect on the int[] x array. My answer was x[0]:5 x[1]:3. I was almost certain that I got the correct answer and when I saw that I had been marked wrong, I got confused. I went to try out the actual code on NetBeans and realized that the values in the array actually got swapped! I then went on to test if this was the case for String. I typed in a similar but different code:  public class Switch {     public static void switch(String s){         s = "GOODBYE";     }      public static void main(String[] args){         String x = "HELLO";         switch(x);         System.out.println(x);     } }   The output still printed HELLO instead of GOODBYE. Now my question is why does the method not change the String but it changes the values inside an array?

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?


Background  This feature request is strongly related to , but the underlying intentions – as well as the specific request – are different.  The bug report  only addresses automatically generated links, not links using Markdown syntax.  Motivation  The character limits are in place to prevent users from posting comments that are either too short or too long. But the length of a comment, for most practical purposes, depends on the amount of text that's being displayed.  As it is, the following comments are too long:      This is a comment linking to a lot of , ,  and . Some of the s are rather long.     s don't have to be long to exceed the  on  if the  is used.    To add insult to injury, the following comments are valid:      This is a huge wall of text, possibly from a user rambling about something he should have either said in an answer of his own or kept quiet altogether. Since there are so many words – and you can't use paragraphs in comments – it separates 1) different points 2) in several 3) sequentially numbered 4) but equally obnoxious 5) list items. By now, you probably have lost interest and stopped reading, or you're silently hoping for the audio version narrated by Jeremy Irons, the soothing voice of Scar from The Lion King. Lion King? Hyenas? Wasn't there a song? Must stay focused and finish reading...         The 600 character maximum is too restrictive when posting links (let alone links with title attributes).  @Shog9 suggested in  to simply increase that maximum, but the current maximum already allows almost unbearable walls of text.  Also, the link syntax might only one of the many ways to circumvent the 15 character minimum, but it's probably the most widely known. Users should at least learn proper Unicode to be able to do that!  Request / TL;DR  In comments, when posting links using the [text](URL) or [text](URL "title") syntax, don't make the URL and title count towards the existing character limits (both maximum and minimum).  To prevent potential abuse of this feature, limit the overall count of characters to 1500.

This is a minor frustration, but I have a  that I put italics and bold into (using asterisks.)  Now I know I just just be happy that I could do it at all, but it seems to me that those should not count toward my comment char limit.


I have used Xubuntu 16.04 fine for months. Today i updated some snapd package, then i restarted the system as required. And now it just won't let me log in. It replies invalid password. I tried to switch to lxde, then a tried to log in to another user account (including root) to no avail.    Then i pressed Ctrl + Alt + F1 to enter the CLI environment. Tried to log on (as regular user, then as root) and i keep getting the same message:      System is booting up. See pam_nologin(8).     I found out that pam_nologin means Prevent non-root users to login. And yet i can't log in as root! What can i do? Should i reset root password from a Live Ubuntu?    P.S. I'm so upset i'm not even looking for my Live Ubuntu and i'm writing this from Windows :( .

I'm working on a Ubuntu system, and my client has completely forgotten his administrative password. He doesn't even remember entering one; however it is there.  I've tried the suggestions on the website, and I have been unsuccessful in deleting the password so that I can download applets required for running some files. Is there a solution?


The widely used word "homophobia" clearly doesn't fit the criteria.  For example, "racism"  can mean discrimination towards any race, black,  white,  Asian,  etc. Similarly, the word we are looking for should also be able to describe people who have prejudice towards asexuals,  bisexuals,  heterosexuals, pansexuals, etc.   Also,  phobia means fear,  or negative feelings. If someone assumes a black man is a fast runner, loves water melon,  and is a great dancer before they have even met him or heard anything about him, simply because he is black,  I would argue that that is racist.  But those are all positive traits,  and therefore there need not be any "phobia"  involved.  Similarly, if one assumes a gay man speaks in a feminine voice, is very knowledgable about fashion,  interior design, etc. and listens to Village People, I would consider that [insert the word we are looking for here]. But there need not be any "phobia" or negative feelings involved, since those traits can all be seen as positive traits.   Repeating the earlier point, the word we are looking for should also describe prejudice against asexual, or even heterosexual people. Asexuality can also be considered a sexual orientation. Clearly,  the word "homophobic" can not be used to describe prejudice against asexual or heterosexual people.   Edit: While the linked question is quite similar, this question is wider and more detailed.

Is there a term that is similar to sexist or racist but refers to gay people? "Homophobic" comes to mind, but that's more a fear or disgust of homosexuals versus discrimination based solely on sexual orientation.  To be specific, I'm looking for an -ist/-ism word, but I'm not sure if one exists.


I am a beginner in android studio. I am working on a quiz app . The app should check for two strings to be compared and give the correct answer. But comparing the two strings (even though if they are same) is not giving the correct output. Instead it is directly going to the final return statement in the code. Here’s the code:  // ... EditText Answer1 = (EditText) findViewById(R.id.answer1); String ans = Answer1.getText().toString(); Log.v("MainActivity", "City name :" + ans); String answer= String.valueOf(Answer1); // ...  public String YourAnswers(String ans, boolean isDT, boolean isHC, boolean isBO,String answer) {      String Message = "1.:You answered  \n"+ans+  "\n"    +ques1(answer);     Message = Message + "  \n 2.:  \n" +question2(isDT,isHC,isBO) ;     return Message; }  public String ques1(String answer) {     if (answer == "Jefferson City"){//||ans=="Jeff City"||ans=="Jeffcity"||ans=="Jeffersoncity"){         return "correct";     }     else if(answer =="Jeff City") {         return "correct.";     }     else if(answer =="Jeffcity"){         return "correct..";     }     else if(answer.equals("Jeffersoncity")){         return "correct.....";     }      return "Sorry,but the correct ans is Jefferson City"; }   When it enters into ques1(), it is directly going to the last statement i.e. return "Sorry,but the correct ans is Jefferson City";. When I enter the correct answer too it is returning the above mentioned line.  Any ideas as to why this might be happening?

I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug.  Is == bad? When should it and should it not be used? What's the difference?


For an SVM classifier, how can I get the confidence of each prediction ? I thought of adding a "unknown" class, but I don't quite see how to do it ( what values ?)  While theory is highly appreciated, I would be glad if you can give me hint(s) on how to do it in scikit-learn.

I have two classes (say 1 and 0), and want to build a classifier. It is possible to use artificial neural networks (ANN) or any "real" classifying method such as SVM or Random Forest. In case of ANN, one can easily estimates confidence level of classification. For example, if we have binary task (with outputs as 0 or 1), and ANN results for some sample is 0.92, one can suppose that ANN "sure" in classification to 1 class. Alternatively, if ANN outputs 0.52, it is considered as unsteady classification to 1 flass.  But if we use Random Forest or SVM how it is possible to confidence level of classification?


Can anyone help to find a formula for this?     $$\sum_{k=1}^n\frac{k}{(1+r)^k}=\frac{1}{1+r}+\frac{2}{(1+r)^2}+\frac{3}{(1+r)^3}+\cdots+\frac{n}{(1+r)^n}.$$   I cannot seem to use $\dfrac{n(n+1)}{2}$ in anyway.

I want to know the general formula for $\sum_{n=0}^{m}nr^n$ for some constant r and how it is derived.  For example, when r = 2, the formula is given by: $\sum_{n=0}^{m}n2^n = 2(m2^m - 2^m +1)$ according to   Thanks!


I am studying  projective modules, but I can't understand why the direct product of projective modules need not be projective in general. Can anyone give me such example? Thanks for any help.

I am looking for an elementary example of a family $\{M_\alpha\}_\alpha$ of projective $R$-modules whose direct product is not projective. The simplest example that I know is the $\Bbb{Z}$-modules, $\Bbb{Z}, \Bbb{Z}, \Bbb{Z}, \cdots$ whose product is not free and hence not projective (as $\Bbb{Z}$-module) but this example uses the fact that $\Bbb{Z}$ is a hereditary ring or something equivalent to that which (in my opinion) is not that elementary. So, I would be grateful if somebody can come up with a simpler example I mean an example that requires as less as possible advanced algebra.


One of my web pages is giving me an:  GET url_plus_query_string_go_here 500 (Internal Server Error)   type of error.  How do I set the page/server up so I can log these errors to find out more about them and why they are happening?

I'm currently using log4net in my ASP.NET MVC application to log exceptions.  The way I'm doing this is by having all my controllers inherit from a BaseController class.  In the BaseController's OnActionExecuting event, I log any exceptions that may have occurred:  protected override void OnActionExecuted(ActionExecutedContext filterContext) {     // Log any exceptions     ILog log = LogManager.GetLogger(filterContext.Controller.GetType());      if (filterContext.Exception != null)     {         log.Error("Unhandled exception: " + filterContext.Exception.Message +             ". Stack trace: " + filterContext.Exception.StackTrace,              filterContext.Exception);     } }   This works great if an unhandled exception occurred during a controller action.  As for 404 errors, I have a custom error set up in my web.config like so:  <customErrors mode="On">     <error statusCode="404" redirect="~/page-not-found"/> </customErrors>   And in the controller action that handles the "page-not-found" url, I log the original url being requested:  [AcceptVerbs(HttpVerbs.Get)] public ActionResult PageNotFound() {     log.Warn("404 page not found - " + Utils.SafeString(Request.QueryString["aspxerrorpath"]));      return View(); }   And this also works.  The problem that I'm having is how to log errors that are on the .aspx pages themselves.  Let's say I have a compilation error on one of the pages or some inline code that will throw an exception:  <% ThisIsNotAValidFunction(); %> <% throw new Exception("help!"); %>   It appears that the HandleError attribute is correctly rerouting this to my Error.aspx page in the Shared folder, but it is definitely not being caught by my BaseController's OnActionExecuted method.  I was thinking I could maybe put the logging code on the Error.aspx page itself, but I'm unsure of how to retrieve the error information at that level.


Show that if $e_n$ is an orthonormal basis for a Hilbert space $H$, and $T:H\to H$ is a bounded linear operator that satisfies $$\sum_{n=1}^{\infty}\lvert\lvert Te_n\rvert\rvert^2<\infty$$, then $T$ is compact. I need to do this by defining a sequence of finite rank operators $T_k$, and showing that $\lvert\lvert T-T_k\rvert\rvert\to 0$, so I know my $T_k$ will probably be of the form $\sum_{n=1}^k...$ and need to end up with something like $\lvert\lvert T-T_k\rvert\rvert\leq\sum_{n=k+1}^{\infty}\lvert\lvert Te_n\rvert\rvert^2\to0$ but I've tried loads of things for $T_k$ such as $T_k(x)=\sum_{n=1}^k\langle x,e_n\rangle Te_n$ but couldn't get anywhere. I have that $\lvert\lvert (T_k-T)x\rvert\rvert^2=...=\langle\sum_{k+1}^\infty\langle x,e_n\rangle Te_n,\sum_{k+1}^\infty\langle x,e_n\rangle Te_n\rangle$ and I tried to simplify this much more but since $Te_n$ aren't orthogonal it's more difficult than usual

Let $H$ be an infinite-dimensional separable Hilbert space and $(e_n)$ an orthonormal basis of $H$. $T\in B(H)$ is called a Hilbert-Schmidt operator if $\sum_{n=1}^{\infty} ||Te_n||^2 < \infty$. I want to show that every Hilbert-Schmidt operator is compact. I am not getting the idea how to use the separability and if it doesn't matter whether the space is infinite or finite-dimensional. But I know that if there is a series of compact finite rank operators that converges to T, then T is compact. *I saw many versions of similar questions with different contexts.


I'm after a nice method to draw from a range of integers given known prior probabilities.   Say I wanted an 80% chance of drawing 1, a 15% chance of drawing 2, and a 5% chance of drawing 3...  I'm obviously thinking about this wrong, since neither   [~,I] = max([.80 .15 .05] .* rand(1,3))  nor  [~,I] = max([.80 .15 .05] + rand(1,3))   appears to achieve this...(rand samples from a uniform distribution)  Does anyone have a suggestion that will extend to any range of integers?  ** Additional Comment **  I realise now for rational probabilities it's trivial just to create a vector comprised of these options proportionally (80% 1s, 15% 2s, and 5% 3s), and then just randperm the contents of the vector and choose the first element over and over...   This method is bad if the probabilities do not behave nicely...

How do I generate numbers based on an arbitrary discrete distribution?  For example, I have a set of numbers that I want to generate. Say they are labelled from 1-3 as follows.  1: 4%, 2: 50%, 3: 46%  Basically, the percentages are probabilities that they will appear in the output from the random number generator. I have a pesudorandom number generator that will generate a uniform distribution in the interval [0, 1]. Is there any way of doing this?   There are no bounds on how many elements I can have, but the % will add up to 100%.


How do I know if I should be using int32_t or uint32_t?  I have found a few descriptions of them (signed/ unsigned) but that hasn't helped me understand this much coming from a java background. So under which scenarios would I use these two options? Specifically I need a variable to hold a 32 bit binary value, but a general answer would be fine as well.

When is it appropriate to use an unsigned variable over a signed one? What about in a for loop?  I hear a lot of opinions about this and I wanted to see if there was anything resembling a consensus.   for (unsigned int i = 0; i < someThing.length(); i++) {       SomeThing var = someThing.at(i);       // You get the idea.   }   I know Java doesn't have unsigned values, and that must have been a concious decision on ' part.


Sadly, SE doesn't have anymore the list of all their paid employees, so I can't verify that there is someone dedicated to this. Yet the recent events on off platform venues and the response of SE as company seems to be that there isn't a real coordination on the public off platform face of the company.  SE seems to have a very large team of community managers, but these are usually dedicated to manage SE own community, but no one to manage the communities that interact with SE outside of SE. This seems to be an oversight.  focus on the engineering and product selling aspects of SE. But this aspect of the business, the one that has to deal with off platform interactions, seems to be fallen into whoever employee happens to see and be able to respond to those.  Sometimes you have to deal with clients that don't really use the site as more engaged individuals nor pay for its use. Lets be serious and get someone to be a measured and corporate face to people that isn't the core clients.  This person should have close relationships with SE CM's. corporate, devs and sales/marketing. Remember this would be a person to represent the company to those outside of it, and having uncoordinated messages at all these levels was the thing this person is set to solve

I don't particularly think I can add more to what Monica's said about what went wrong, and . Things could have gone better. I don't really see people getting any happier about it.   I'd like to ask for a few things going forward.   Firstly - that a community team member should be dealing with social media criticisms, and we really should also be giving our communities the benefit of the doubt. In situations like this - something like "Hi! We've noticed you have an issue with the content you see on SO's sidebar. We'll see how we can help" would have been a better starting point than knocking a site off HNQ. Under most circumstances, I'd actually trust Adam - as a former community team member - to deal with it, but in this situation, we basically had folks from two different teams that don't actually deal with users directly in such circumstances try to help, in good faith and, well it didn't work that well. We need to have someone specifically dealing with these things.     We also need a clear idea of how the folks who deal with these things need to engage with the affected communities if action is taken.   For most part, the community team's had to do damage control when they're the folks who should have been dealing with it. I do realise in the past few years they've basically been pulled in 20 different directions and have been constantly dealing with backlog - but one of the consequences is it feels like the management of SO and SE has been drifting further and further away from the community.   We've constantly been told that we need to make SE better for new users and we need to attract them and grow. I've occasionally accused SE of being short sighted. I think this is one of those situations where I'm starting to feel there's tunnel vision - since the end result of it is folks who would traditionally supported SE feel that traditional methods seem neglected.  You have one of the best community teams I've had the pleasure of interacting with. They're engaged, passionate and some of the best folks I've interacted with on the internet. You'd be down a lot of core users if not for them. They're also smaller than they have ever been, with a smaller team than some medium sized site. (This is a difficult thing for me to talk about - since I've expressed an interest in the role before). We constantly hear promises that they'll improve processes - and that they'll tackle the backlog. And what we really really really need is people on the ground listening. "Hey guys, so someone has issues with the site. Could you guys tell us what you think? Could we do something about it?" goes so much further than anyone realises.  We've been really really patient, but we shouldn't need to tweet at folks to get your attention. We've been really patient. We really would love SE to grow, but not at the expense of its heart.


i'm duplicating an object with Array but the object itself has a lot of geometry, so my computer slows down a lot, is there any solution to this, like adding more ''copies'' as instances?  Thanks in regard.

When I composed my     I would have liked to have the camera pitch up enough to show the horizon, except I didn't have enough geometry to extend the cobblestone street and the sidewalk all the way to infinity (mostly because that would require infinite stuff).  Even in that shot it is clear that I need to widen the "sidewalk" to cover up the "sky"box.    Contrast with     where the ray tracer can use the procedurally replicated geometry.   is a failed attempt at faking out the horizon, even with low detail.  It fails because lighting's interaction with the geometry gives it away.  Some techniques that prevent you from having to deal with infinity include   put the scene in a box (usually a room) put the scene in a canyon (which is just a box without a top so you can see the relatively featureless sky) route the road into a tunnel, or around a corner and hide the horizon with other geometry (which is really just a variant on the canyon). have no detail on the ground at all (flat color or gradient)   Those are all dodging the question of interest to me:  What techniques have people used in blender to fake various kinds of detail repeating into the distance (instead of just obstructing the view of infinity)?


I've probably read it somewhere in Sakurai but I cannot recall it at the moment. So how does one really measure the proton's spin? I mean the proton's spin and not its constituents.   Do you measure it using a Stern-Gerlach type of setup?  How about atoms and other stuff, how is their spin measured?

If I've got an instance of a fundamental particle, how can I separate out the measurements of these four quantities?  (I think) I understand the theory behind them, and why the particles in the standard model are predicted to have the values they do. However, the process of validation of these numbers eludes me. How have they been historically measured?


I love Skyrim. I especially love the horses. And I want Shadowmere to be my horse. I was just wondering if it is possible to have Shadowmere, and spare Cicero, while also destroying the 'Dark Brotherhood'.

I know that  is a quest reward from the Dark Brotherhood questline. However, since I took the other route, killed Astrid when she visited me and got the quest to destroy the Brotherhood, which I later did (she can't tell me what to do!), I was wondering if it's still possible to get her horse some other way and not through the quest.


I've got about 1000 filenames read by os.listdir(), some of them are encoded in UTF8 and some are CP1252.  I want to decode all of them to Unicode for further processing in my script. Is there a way to get the source encoding to correctly decode into Unicode?  Example:  for item in os.listdir(rootPath):      #Convert to Unicode     if isinstance(item, str):         item = item.decode('cp1252')  # or item = item.decode('utf-8')     print item

I received some text that is encoded, but I don't know what charset was used. Is there a way to determine the encoding of a text file using Python?  deals with C#.


I am using a different computer than mine. I cannot get to my Google Account because that's the account of my brother which is registered.

It only shows one of my Google accounts. I want to log into a different one but I don't want them connected in any way. What do I do?


Was it possible for Lord Voldemort to look directly into the Basilisk's eyes when he opened the chamber of secrets? Or did he take precautions?

We see in the Chamber of Secrets when Tom Riddle summons the Basilisk, he looked at the Basilisk's eyes directly.     So are they immune to the effects, or is it just the controller?


When installing Ubuntu 18.04+ (and other modern distros), do I still need to create a SWAP partition?

I'm  installing Ubuntu on a Samsung evo 850 SSD drive. System has 4GB memory but no other harddrive. Should I use thedefault partition table or install without swap and make a swap file after installation? Or does it even make a difference whether it’s a partition or a file?


I played the destiny beta at 2pm and 5pm. I didn't play the event, I didn't know it was going on. I was signed in and just messed around in old Russia.   Do I get a nameplate or any reward?

In the beta you were supposed to receive an nameplate if you played at 2:00 pm PDT. I got a message saying public event and clicked it but received no nameplate. Do I not get it until the full game or has my game glitched and I just can't get it.


I just installed Ubuntu Saucy with unity on an Acer C720.  I downloaded Software Center from Synaptic and when I type in gksu software-center I get the error, Failed to load module "canberra-gtk-module."  I also tried the following:  sudo apt-get install libcanberra-gtk-module sudo apt-get install libcanberra-gtk-module:i386   For both, I get the following:  E: Unable to lock the administration directory(/var/lib/dpkg/), is another process using it? E: Could not get lock /var/lib/dpkg/lock - open (11:resource temporarily unavailable)   I am brand new to Ubuntu, so any help would be greatly appreciated.

I get this error when trying to use apt-get:  E: Could not get lock /var/lib/dpkg/lock - open (11 Resource temporarily unavailable) E: Unable to lock the administration directory (/var/lib/dpkg/) is another process using it?     How can I fix this?


So we let $S,T : \mathscr{C} \rightarrow \mathscr{D}$ be naturally isomorphic functors. We seek to show that if $S$ is a full functor, then so is $T$.  As given, we have a natural isomorphism $\tau : S \rightarrow T$, which also means that each component of it $\tau_A : S(A) \rightarrow T(A)$ is invertible.  From here, though, I get pretty lost and have no clue where to go. I'm not even 100% sure how to best show surjectivity in the context of category theory. I feel like that I would have to use the inverse of the natural transformation, $\tau^{-1}$, and that surjectivity implies right-cancellativity, i.e. $S$'s arrow function has a right-sided inverse $S^{-1}$. But I'm honestly just lost.  Does anyone have a potential nudge in the right direction?

If $F,G: C \rightarrow D$ are functors between regular categories and $F \Rightarrow G$ is a natural isomorphism, is it true that if $F$ is faithful {resp. full) then $G$ is full?  I believe this is true but would like some confirmation.  What about if $F$ is essentially surjective?  Is it necessarily true that $G$ is essentially surjective?  Thanks.


I would like to play with my friend on Minecraft PE, but when we connect to the same network, I can't detect his world when he opens his world, and he can't find my world on LAN when I open my world. Does it have to do with the firewall. I went to another friends house and connected to their network and it worked! So what should I do?

I can't find how to join games with the latest 0.7 Pocket Edition update with an iPad and iPod over wifi. I see the realm options but I get the message "there are no more open server slots right now". Local server multiplayer is switched on for both devices.


$\bullet \textbf{ Explanation}$  A "substrime" is a prime in which all substrings are prime. The number $373$ is an example since $3,7,37,73,$ and $373$ are each prime numbers. In decimal (base-10) the only substrimes are: $$2,3,5,7,23,37,53,73,373.$$ See:   But we can look at substrimes in any base. For example in base-5 the substrimes are $$2,3,23,32,232.$$  There are $103$ substrimes in base-24 the largest of which is  $$266003=(19)(5)(19)(11)|_{24}.$$  We computed these up to base-100 and found base-90 had the most; $1455$ in total (live code: ).  $\bullet \textbf{ Question}$  Does any base have infinitely many substrimes?  $\bullet \textbf{ Attempt}$  Every substrime of $n$ digits can be thought of as two substrimes on $n-1$ digits such that cutting off the leftmost digit of one and the rightmost digit of the other give a substrime of length $n-2$. For example, in base $28$ the substrime  $$(11)(3)(23)(3)|_{28}=244471$$  has $4$ digits. It can be viewed as the substrimes $$(11)(3)(23)|_{28}=8731\quad\text{and}\quad(3)(23)(3)|_{28}=2999$$ which share a common substrime $(3)(23)|_{28}=107$ obtained after truncation.  So let "$S_b(n)$" mean "the amount of substrimes with $n$ digits in base $b$". From the previous bit we obtain two inequalities  $$(1)\quad S_b(n)\le S_b(1)\cdot S_b(n-1)$$ $$(2)\quad S_b(n)\le S_b(n-1)^2$$ which paired with the prime number theorem gives us heuristics $$(1)\quad S_b(n) \approx \frac{S_b(1)\cdot S_b(n-1)}{n\log b}=C_b\frac{S_b(n-1)}{n}$$ $$(2)\quad S_b(n)\approx C_b'\frac{S_b(n-1)^2}{n}$$  Thus we would expect $S_b(n)$ to hit zero eventually since the numerator grows at best like O$(n^2)$ but the denominator grows like O$(n!)$.  But of course, this is hueristic. It seems also highly composite bases have more substrimes. For example, the record holder bases with the most susbstrimes are: $$3,4,5,7,8,12,18,24,30,42,48,54,60,90,...$$  Here is a chart:   I was unable to determine why composite bases have more substrimes.

For no particular reason I stumbled upon the sequence/set of all numbers where all substrings of the decimal representation is prime (A085823). It's quite easy to see that this must be a finite set. My approach was that the digits must alter between 3 and 7 eventually (since a prime can't end with 2 or 5 for larger than that and a prime can't consist of just two non-1 digits, those would be dividable by 2, 5 or 11) and we can see where it ends.  But if we change the base that approach fails. For example in base 8 a prime can end in 3, 5 or 7 AFAICS so such numbers can end in a altering sequence of 3, 5 and 7s but having tree digits to alter between there's always a way to vary the sequence.  I tried to write a python snippet to produce such numbers in different bases and for those I've tested the program seem to hang (ie don't seem to find any more numbers). Is it true that there are only a finite number of such numbers for every base?


I'm reading Andrew Ng's note about  He writes the likelihood of data as  where random variables $z^{(i)}$'s indicate which of the $k$ Gaussians each $x^{(i)}$ had come from. Then he says that if we knew what the $z^{(i)}$'s were, the maximum likelihood problem would have been easy. Specifically, we could then write down the likelihood as  I could not get this last step. If we knew what the $z^{(i)}$'s were, then shouldn't we just need to calculate the likelihood from the Gaussian distribution (I understand that if we knew $z^{(i)}$'s we do not need to take a weighted sum over $k$ Gaussians but why do we still need to multiply with the probability of the known $z^{(i)}$, i.e.,  $p(z^{(i)};\phi)$)? In other words shouldn't the likelihood be as below:  There is a similar question  but it does not answer my question.

I'm trying to make sense of a derivation I'm following from the lecture notes of Stanford's ML course.  Specifically the notes are here:   I'm particular I'm interested in the step where they are optimizing the lower bound of the log-likelihood by finding the derivative of that function w.r.t the mean (top of page 7). I'm a bit stuck on going from line 1 to line 2 in that sequence.  To copy here (using abbreviated notation for space):  $$ \nabla \mu_s \sum_{i=1}^{m}\sum_{j=1}^{k} w_j^{(i)}\log\frac{\alpha_j \exp\psi_{j}^{(i)}\phi_j}{w_j^{(i)}}  \qquad(1) $$ $$ \nabla \mu_s \sum_{i=1}^{m}\sum_{j=1}^{k} w_j^{(i)}\psi_{j}^{(i)}\qquad(2) $$ where $\psi_{j}^{(i)} =-\frac{1}{2}(x^{(i)}-\mu_j)^T\Sigma^{-1}_{j}(x^{(i)}-\mu_j)$ and $\alpha_j=\frac{1}{(2\pi)^{n/2}|\Sigma_j|^{1/2}}$.  The quantity $\mu_s$ is the mean (of a multivariate gaussian distribution) for class $s$.    In short, I'm not sure how they get from (1) to (2).  From just changing the log of (1) I see:  $$ \nabla \mu_s \sum_{i=1}^{m}\sum_{j=1}^{k} w_j^{(i)}\log \left(\alpha_j \exp\psi_{j}^{(i)}\phi_j\right) - w_j^{(i)}\log w_j^{(i)} \qquad(1) $$  To get to their form (2) my impression is that they take pre-emptively discard terms that would contain derivatives of $w_j^{(i)}$ (w.r.t. $\mu_s$).  At least if you assume that much, you get to (2).  However, as they show earlier in that PDF,  $$ w_j^{(i)} = p(z^{(i)}=j | x^{(i)}) =\frac{p(x^{(i)}|z^{(i)}=j)p(z^{(i)}=j) }{\sum_j p(x^{(i)},z^{(i)}=j) } $$ i.e. this quantity is the posterior distribution of the class labels.  Intuitively, it seems like $\partial w_j^{(i)}/ \partial \mu_s$ should be non-zero.  After all, changing the location of the mean $\mu_s$ would change your posterior probability for a particular class given the same data.  (Right?).  Just from a mechanical point of view, $\partial w_j^{(i)}/\partial \mu_j$ would seemingly have some non-zero terms since $p(x^{(i)}|z^{(i)}=j) \sim \mathcal{N}(\mu_j, \Sigma_j)$.  If I work through the algebra, I get  $$ \frac{\partial w_j^{(i)}}{\partial \mu_j} = w_j^{(i)}(1-w_j^{(i)})\frac{\partial \psi^{(i)}_{j}}{\partial \mu_j} $$  What am I missing here?  If I take the log-likelihood (without even thinking about EM algorithm),    $$ \ell = \sum_{i=1}^{m}\log \sum_{j=1}^{k}p(x^{(i)}|z^{(i)}=j)p(z^{(i)}=j) $$ and differentiate w.r.t $\mu_s$, I correctly get  $$ \mu_s^* = \frac{\sum_{i=1}^{m}w_s^{(i)}x^{(i)}}{\sum_{i=1}^{m}w_s^{(i)}} $$  so I'm comfortable with the eventual result, just not the intermediate steps.


Is there a way to put a decimal field on a visualforce page and allow the user to update it?  I'm able to display as OutputText per below but I would like the user to be able to change.    <apex:OutputText value="{0, number, 00.00}" Label="CMS%">   <apex:param value="{!Applicant__c.CMSP__c}" />    </apex:OutputText>   Thanks, Ed

My VF tags:  <apex:column >     <apex:facet name="header">Sales Price</apex:facet>     <apex:inputText value="{!prod.SalesPrice}"/>     </apex:column>   Controller code:  public string SalesPrice{get; set;} oli.UnitPrice =decimal.valueOf(pi.SalesPrice);   It works when a user insert 15 and 15.00 but it doesn´t with 15,00(comma).  I m using apex:inputText linked to a controller apex property because apex:inputfield is not allowed.  I´ve tried with apex:input with type=number but it doesn´t look good, (small button to increase/decrease inserted value). Is there another Visualforce tag that i can use with a property? Is the only solution to replace comma with dot in the controller?


I have designed a specific client and server program, which sends a file  from client to server in 32k chunks. I want to encrypt only part of the data. More specifically: in each 32k chunk passing from client to server I want to encrypt only 500 bytes. This, in a non-continuous way (meaning: partial encryptionhere and there in the chunk of 32k, totally forming 500 bytesof encrypted data within the 32k block). Here client is a constrained sensor and server is an Arduino board used for Internet of Things concept, to save of energy of the constrained device(client) i want to encrypt only parts of data.  Are there any lightweight(here refers to C.P.U consumption) cryptographic algorithms or methods which offer  the option to set an “offset” and a parameter defining how much partial data we want to encrypt?  For example encrypt (bufptr, random_num, ENCRYPT_LENGTH); where bufptr is a 32k chunk with information, random_num is the random number smaller than the bufptr pointing to the bufptr, ENCRYPT_LENGTH is the length we want to encrypt (like 20 bytes from the number pointed by the random_num).

Some time ago I was working in a pet project for a type of database engine. And I thought about securing the data in disk with encryption.. and since the main code was already developed.. I had a few requirements..   a simple stream class that I could hook instead of my file stream had to support random access (both read/write at random positions) be able to work at any byte position (since the data might not be aligned) encrypt/decrypt only the requested data, not the all file,(because the file maybe several MB) fast encryption/decryption, since this was for a database system   nowhere on the web I found information about this, or implementation of such code. Normal stream ciphers don't support random access/lookup, and block ciphers require the data to be aligned and in fixed blocks..  So I thought about developing my own. I do know that developing your own encryption is always a bad choice.. but this was kind of theoretical exercise..  So I would like to present you the code.. just to see how far of I am from a security point of view  First the stream is initialized with a password.. but that password is not used for the encryption itself.. it is used as a seed to scramble an array of 256 values in hope of of increasing the key space  public CipherStream(String sKey,Stream oStream)  {     _oStream = oStream;     //initialize key space     _oVector = new byte[256];     for(int i = 0; i <= 255; i++)     _oVector[i] = (byte)i;     //shuffle the keyspace     for (int i = 0; i <= 255; i++)//shuffle the box     {         //shuffle this item with other         //other is chosen by char(i) of password         //and the currently shuffling vector(I)         // this means that even repeating passwords 'aaaaaa' will produce random results         int j = ((sKey[i % sKey.Length]) + _oVector[i]) % 256;         byte cTemp = _oVector[i];         _oVector[i] = _oVector[j];         _oVector[j] = cTemp;     } }   after this all we have to do is choose the cipher byte for the position we are trying to read/write from.. in my implementation I used xor, witch I know is not the most safe.. but that is can be changed and is not the core of the algorithm..  public override void Write(byte[] buffer, int offset, int count) {     long nPosition = this.Position;     for (int i = offset; i < count; i++)     {         byte oPlain = buffer[i];         byte nKey = GetKey(nPosition);         byte oCypher = (byte)(oPlain ^ nKey);          buffer[i] = oCypher;          nPosition++;     }     _oStream.Write(buffer, offset, count); }   the 'key' to the byte is chosen from the key vector dependently from the position we are trying to access.. calculations are done so that there are no repetitions and the chosen value is as random as possible  private byte GetKey(long nPosition)  {     byte nOffset = _oVector[nPosition % _oVector.Length];     byte nOffset2 = _oVector[(nPosition / (nOffset + 1)) % _oVector.Length];      int nDif = nOffset - nOffset2;     if (nDif < 0)         nDif += 255;     byte nKey = (Byte)(nDif % 256);      return nKey; }   I did try to render the stream as a bitmap.. just so make sure no patterns where obvious.. and did some fine tunning there.. and it seemed ok..  the best I can describe this algorithm is a 'deterministic predictable pseudo-random generator' where I can just ask 'give me the nth random number', and the seed is a 2048 bit vector that is initialized randomly with a password..  how far am I from a solution? Is this completely insecure? or there is not even point of trying because there is no solution for this 'random access stream'  problem?


Q. A square tower stands upon a horizontal plane. From a point in this plane, from which three of its upper corners are visible, their angular elevations are respectively are 45 ∘ ,60 ∘ , and 45 ∘. Show that the height of the tower is to the breadth of one of its sides as  √6 ( √5 + 1) to 4. I am not able to imagine the diagram of the situation. Moreover, isn't it that the ratio of height of a square to its breadth is the same as ratio of diagonal to its side i.e. √2/1

Is there an easier way of doing this problem:     A square tower stands upon a horizontal plane. From a point in this place from which three of its upper corners are visible their angular elevations are respectively  45°, 60° and and 45°. Show that the height of the tower is to the breadth of one of its sides as $\sqrt{6}(\sqrt{5}+1)$ is to 4.     I'm not sure if my approach is  correct since it seems that to get the result using the way I've done it isn't as simple as previous questions have been (a few lines of working). In the digram $a$ is the length of the side of the tower and $h$ is the height of the tower. To start I tried to find $x$ in the diagram: $$ h^2=\frac{a^2}{2}+(x+\frac{\sqrt{2}a}{2})^2 $$ which already isn't very straight forward to find $x$ but I was using Mathematica just to see if this method would eventually work which gave $x$ to be:  $$ x=\frac{1}{2} \sqrt{4 h^2-2 a^2}-\frac{a}{\sqrt{2}} $$ which if we then use the top right triangle that $\tan{60^\circ}=h/x$: $$ \sqrt{3}=\frac{h}{\frac{1}{2} \sqrt{4 h^2-2 a^2}-\frac{a}{\sqrt{2}}}$$ which simplifies to give (well it reduces to this according to Mathematica, I can't seem to easily do it, but since I'm convinced there's an easier way I didn't spend too long on it.): $$ a=\frac{h(\sqrt{5}-1)}{\sqrt{6}}$$  and after a little rearrangement this gives what seems to be the required result: $$ \frac{h}{a}=\frac{\sqrt{6}(\sqrt{5}+1)}{4} $$  Is there any easier way to do this since this since this can't be the simplest way (I seem to be quite good at overcomplicating things a little too often!)?


Cardinality of continuous functions $f:\Bbb R\to \Bbb R$.   We know that a continuous function $f:\Bbb R\to \Bbb R$ is completely determined by its values on $\Bbb Q$.  For each rational $q\in \Bbb Q,f(q)$ has $c(=\text{Card }\Bbb R)$ many choices.  Hence the number of such functions becomes $\mathfrak{q^c}= \Bbb N^c$ .  Is it right?Please check.

I believe that the set of all $\mathbb{R\to R}$ continuous functions is $\mathfrak c$, the . However, I read in the book "Metric spaces" by Ó Searcóid that set of all $[0, 1]\to\mathbb{R}$ continuous functions is greater than $\mathfrak c$:  "It is demonstrated in many textbooks that $\mathbb{Q}$ is countable, that $\mathbb{R}$ is uncountable, that every non-degenerate interval is uncountable, that the collection of continuous functions deﬁned on  $[0,1]$ is of a greater cardinality than $\mathbb{R}$, and that there are sets of greater and greater cardinality."  I understand that (via composition with the continuous function $\tan$ or $\arctan$) these sets of continuous functions have the same cardinality. Therefore, which claim is correct, and how do I prove this?


HashMap myMap = new HashMap<Character, Character>();  Map myMap = new HashMap<Character, Character>();   What is a more technical way to describe the difference between the two above lines of code, in terms of object oriented programming and polymorphism during an interview?  A non technical way seems like it would be:  The left side of the equals sign is how we "talk" to the object, the right said is what the object actually is.  The left side could be an interface, but the right has to be an instantiable class since we can't instantiate an interface.

I have seen this mentioned a few times and I am not clear on what it means. When and why would you do this?   I know what interfaces do, but the fact I am not clear on this makes me think I am missing out on using them correctly.   Is it just so if you were to do:  IInterface classRef = new ObjectWhatever()   You could use any class that implements IInterface? When would you need to do that? The only thing I can think of is if you have a method and you are unsure of what object will be passed except for it implementing IInterface. I cannot think how often you would need to do that.   Also, how could you write a method that takes in an object that implements an interface? Is that possible?


I have 349 rep and the system will let me vote to re-open a question although I saw somewhere else on Meta Stack Exchange that you need 3,000 rep to be able to cast close/re-open votes. It says I have earned the "View close votes" privilege but I thought that was only viewing close/re-open votes and not casting them. It was a pe-open vote on my own question, if that makes a difference.  What is going on here?

I just had one of my questions closed. (Hey - it happens to everyone) When I clicked on reopen - lo and behold - it worked. I cast a reopen vote!  Is this a glitch? I know we need 4 more votes anyway but still...  And no  tag please :)


Would to tell me  difference between the its and it's please

While I know technically the English language has a distinction because when there's a conflict between the possessive form and a contraction, the contraction wins. That is:   Its is the possessive form of it—and this will presumably be followed by some form of noun spec or something. It's is short for "it is" or "it has" (as in "it's been years since...").   The rule of thumb I use to remember this is that it follows the same pattern as whose and who's, for which the correct use is much more obvious.  While technically I see why there's (ha ha) a distinction, I can't think of any case why it really needs to be there, because for every use of either construct, the meaning intended is usually (if not always) obvious from context. Case in point: many questions and answers written on the Stack Exchange network are written incorrectly, yet nobody notices or cares. (Usually in my case, I default to "it's" then realize I screwed up)  As a single word, I could see why it'd be ambiguous, but I don't see why in typical prose it would matter.  Is there a specific reason for this in earlier dialects of English, or specific cases where choosing the incorrect form leads to lack of understanding of a particular sentence?


We have this theorem for square matrices $A,B$ over a field $K$, and $\lambda$ an indeterminate:  If $\lambda I - A$ is equivalent to $\lambda I - B$, then $A$ is similar to $B$. ($A$, $B$ are matrices in $K^{n\times n}$, and $\lambda I - A$ is the characteristic matrix of $A$).  (Note The word "equivalent" above means that you can get one from the other by doing row operations and column operations: a sequence of elementary operations on rows or on columns: add multiple of one row to another, swap two rows, or multiply one by an invertible scalar, or similar operations for columns. In this case the equivalence allows polynomial scalars in $K[\lambda]$). The proof which I'm aware of is very ... "calculation-style": It first proved a lemma, (something like $M(\lambda) = P(\lambda)(\lambda I - A) + R$), then show you the result is correct by doing some calculations. (I think there is good chance that you know which proof I am talking about). After reading the proof, I still have no idea why it is true. Knowing a proof usually helps you understanding something, but for this one, it confuses me. So, my question is: Is there an alternative proof for this theorem, (undergraduate level), that helps me to understand what's going on.

When reading the topic about primary and rational canonical form of matrices I stuck myself on this theorem:     The matrices $A,B\in K^{n\times n}$ are similar if and only if their characteristic $\lambda$-matrices $(A-\lambda{I})$ and $(B-\lambda{I})$ are $\lambda$-equivalent; more precisely if $P(\lambda), Q(\lambda) \in K[\lambda]^{n\times n}$ are invertible such that $(B-\lambda{I})=Q(\lambda)(A-\lambda{I})P(\lambda)$ then $P(\lambda)=P$ and $Q(\lambda)=Q$ are constant matrices satisfying $Q=P^{-1}$ and $B=Q A P$.    (in Slovak).   The main point in the proof of this theorem seems to be the assertion: If $P(\lambda), Q(\lambda)$ are invertible and $(B-\lambda{I})=Q(\lambda)(A-\lambda{I})P(\lambda)$ then $P(\lambda)=P$ and $Q(\lambda)=Q$ are constant matrices.  What is the proof of this assertion?


I faced this error while Runnign Edubuntu from Virtual Box.   I used this edubuntu-13.04-dvd-i386.iso file.

I get this message while trying to install Ubuntu 12.04 as a guest in VirutalBox 4.1.18, on an Ubuntu 10.04 host.         This kernel requires the following feature not present on the CPU: pae   Some host specs:     The host's kernel is: Linux 2.6.32-41-generic-pae GNU/Linux   lscpu (host): Architecture: i686, CPU op-mode(s): 32-bit, 64-bit   grep --color=always -i PAE /proc/cpuinfo   does show pae in its output.   The 12.04 iso used is: ubuntu-12.04.0-desktop-i386.iso      As a comparison/check, I downloaded and installed Linux Mint 13 Cinnamon to the same host on the exact same VM (I just changed the .iso image). It worked fine. Its iso is: linuxmint-13-cinnamon-dvd-32bit.iso   It seems (to me) that I have pae.. what is going on here?   Update: I had assumed that Linux Mint also required pae (being Ubuntu based), but I've just run;   grep --color=always -i PAE /proc/cpuinfo   in the Mint VM.   It showed no output.   So it seems the issue may lie with VirtualBox.   If that is the case, how can I get Virtualbox into pae mode?


I want to make a list of text/buttons that prompts a box with a yes/no-option when the user clicks it. If the user presses yes, they get redirected to another site. If no, they are just prompted with a explaining they can't continue without pressing yes.  This is what I have as of now:    <script type="text/javascript"> <!-- function confirmation() {  var answer = confirm("My message here.")  if (answer){   window.location = "www.google.com";  }  else{   alert("If not, then this.")  } } //--> </script> <body> <form> <input type="button" onclick="confirmation()" value="Go to Google.com"> </form> </body>  <head> <script type="text/javascript"> <!-- function confirmation() {  var answer = confirm("My message here.")  if (answer){   window.location = "https://www.stackoverflow.com";  }  else{   alert("If not, then this.")  } } //--> </script> </head> <body> <form> <input type="button" onclick="confirmation()" value="Go to StackOverflow.com"/> </form> </body>     Unfortunately, this makes both buttons refer the user to stackoverflow.com. It always seem to apply the last "window.location" to all buttons that I add.  I would want each button to link to a different site. Any help is greatly appreciated.

What is the best way(s) to fake function overloading in Javascript?   I know it is not possible to overload functions in Javascript as in other languages.  If I needed a function with two uses foo(x) and foo(x,y,z) which is the best / preferred way:   Using different names in the first place Using optional arguments like y = y || 'default' Using number of arguments Checking types of arguments Or how?


I am trying to create a key and value array from database record, but the array just getting the final record! Here is a snippet of my code:  $cateogiresArr = array(); while ($row = mysqli_fetch_row($result)) {   $cateogiresArr["categoryname"] = $row[1];   $cateogiresArr["description"] = $row[2]; } header("Content-type:application/json"); $json_categories = json_encode($cateogiresArr);

How do I use the json_encode() function with MySQL query results? Do I need to iterate through the rows or can I just apply it to the entire results object?


This is not a duplicate of the following questions     because:  My question specifically states that I am interested in end-user experience, not ease or efficiency of development, which is what the other question largely refers to.  As has been noted, development/deployment affects end-user experience, but it is not all there is to it, and neither of the referenced questions address issues that directly impact an end-user's ability to use the application (e.g. trouble accessing data on other partitions, sluggishness, etc.) Maybe "compelling" wasn't the right word to use; my intent was to ask about real-world, experiential consequences, i.e., things that happen or  don't happen, as opposed to theoretical/architectural statements that, while presumably accurate, don't appear to be backed up with any real-world examples to support the statement. I should have stated more directly that my intention was to get answers that consider the balance of "advantages" to snaps against the real-world downsides experienced by end-users. The "duplicate" question is largely theoretical, and doesn't discuss end-user experience at all. The "duplicate" question makes no mention of anything remotely similar to the example I used here, i.e., that there is an end-user downside to snaps (in this case, lack of access to data on other partitions and snap app performance) that isn't discussed in any available documentation that I can find.   While I understand that snap has a big advantage in making apps more widely available, is there any compelling reason to choose snap over apt, if the app is available for my distro/version via an apt package? I am curious because I've been doing some reading about snaps, and all the excitement about the method seems to be about things that are advantageous for app developers, but I've seen virtually nothing on how this makes life easier for end users (aside from the obvious; that they may be able to install apps that aren't otherwise available on their distro/version). I installed snapd and installed a couple of snaps and was really frustrated and disappointed.  The snap apps are slow and it's difficult, if not impossible, to access files on other partitions from within the snap. While I've seen plenty of info that says snaps are "faster," "easier," "safer," etc., I haven't been able to find anything that explains why or how this is actually the case. Being very new to Linux, I am wondering if maybe I'm just missing something obvious? To be clear, I understand why the technology might be useful overall, but I can't find anything that explains whether/why it is a better option even when the app in question is available for install via a more traditional method, and all dependencies are met.

I have a very little knowledge about the 'Snap packaging format'. What I know is that 'Snap' is an alternative packaging format like .deb.   What I don't know is    Why did Canonical chose it? What are the main advantages of 'Snap' over .deb? Will .deb be abandoned, or is it already abandoned?


Someone was talking about cats and I said I'm not a pet person mainly because of their poops. Then I said: "Just thinking about the smell makes me want to throw up." Even though I said 'about' I feel like I should have said 'of' since thinking about means actively thinking about something and thinking of means you are least aware about it/an idea comes to your mind. Since I don't actively think about cat poops. Should I have said 'of?'

Could someone help me to understand when I should use think of and when think about in sentences?  What is the difference between using one or the other?


Newbie here. I just got an error running from the terminal a C++ program I wrote: error: ‘stoi’ is not a member of ‘std’. They told me the compiler is too old.  I'm using Ubuntu 14.04.  My g++ version is 4.8.4.  How do I upgrade?

System Details:  $ cat /etc/lsb-release DISTRIB_ID=Ubuntu DISTRIB_RELEASE=12.04 DISTRIB_CODENAME=precise DISTRIB_DESCRIPTION="Ubuntu 12.04.2 LTS"   $ g++ --version g++ (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3 Copyright (C) 2011 Free Software Foundation, Inc. This is free software; see the source for copying conditions.  There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.