When I update withsudo apt-get update it comes up with a list of errors:  Reading package lists... Done                       W: The repository 'cdrom://Ubuntu 16.04.3 LTS _Xenial Xerus_ - Release amd64 (20170801) xenial Release' does not have a Release file. N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use. N: See apt-secure(8) manpage for repository creation and user configuration details. E: Failed to fetch cdrom://Ubuntu 16.04.3 LTS _Xenial Xerus_ - Release amd64 (20170801)/dists/xenial/main/binary-amd64/Packages  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs E: Some index files failed to download. They have been ignored, or old ones used instead.   How do I fix this?

Every time I try update (using sudo apt-get update) my Ubuntu I get this problem:  W: The repository 'cdrom://Ubuntu 16.04 LTS _Xenial Xerus_ - Release amd64 (20160420.1) xenial Release' does not have a Release file. N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use. N: See apt-secure(8) manpage for repository creation and user configuration details. W: The repository 'ppa.launchpad.net/kirillshkrogalev/ffmpeg-next/ubuntu xenial Release' does not have a Release file. N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use. N: See apt-secure(8) manpage for repository creation and user configuration details. E: Failed to fetch cdrom://Ubuntu 16.04 LTS _Xenial Xerus_ - Release amd64 (20160420.1)/dists/xenial/main/binary-amd64/Packages  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs E: Failed to fetch cdrom://Ubuntu 16.04 LTS _Xenial Xerus_ - Release amd64 (20160420.1)/dists/xenial/main/binary-i386/Packages  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs E: Failed to fetch ppa.launchpad.net/kirillshkrogalev/ffmpeg-next/ubuntu/dists/xenial/main/binary-amd64/Packages  404  Not Found E: Failed to fetch ppa.launchpad.net/kirillshkrogalev/ffmpeg-next/ubuntu/dists/xenial/main/binary-i386/Packages  404  Not Found E: Some index files failed to download. They have been ignored, or old ones used instead.   How can I fix it? I use Ubuntu 16.04 LTS


I wrote the below code split a String and insert it into a Object Array. But,  I am getting null pointer exception at the below line. Can you please let me know what is wrong in my code. Thanks in advance                     nDLs[i].setDisplayName(entrySplit[1]);   Code:      public class JsonResponse {           public static void main(String[] args) {                String response = "eclac-allfocalpoints@un1.org:ECLAC-All Focal Points|testgrp-icc@un.org:TestGRP-ICC|unon-ictsalerts@un.org:UNON-ICTSAlerts|oict-oict-globalvtc@un87.org:OICT-Focal Points All|";                 NodeDLList nDLList = new NodeDLList();                    System.out.println("RESPONSE::::: " + response);                  String split[] = response.split("\\|");                  NodeDLs[] nDLs = new NodeDLs[split.length];                  for (int i = 0; i < split.length; i++) {                      String entry = split[i];                      String entrySplit[] = entry.split("\\:");                          nDLs[i].setDisplayName(entrySplit[1]);                        nDLs[i].setPrimaryEmail(entrySplit[0]);                  }                  System.out.println("Complete response in Node List Object ::::: " + nDLs);                  nDLList.setdistributionLists(nDLs);                  System.out.println(nDLList);       }     }   NodeDLList.java      public class NodeDLList {            NodeDLs[] distributionLists = null;            public NodeDLs[] getdistributionLists() {             return distributionLists;         }          public void setdistributionLists(NodeDLs[] distributionLists) {             this.distributionLists = distributionLists;         }       }   NodeDLs.java      public class NodeDLs {          String primaryEmail = null;          String displayName = null;          public String getPrimaryEmail() {             return primaryEmail;         }          public void setPrimaryEmail(String primaryEmail) {             this.primaryEmail = primaryEmail;         }          public String getDisplayName() {             return displayName;         }          public void setDisplayName(String displayName) {             this.displayName = displayName;         }

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


Sorry for asking a stupid question. In this context: "A monkey holds a tortoise in his hand when going to the river." Can we say: The tortoise is going to the river? I think the tortoise was delivered, so technically, we can't say that "It was going to the river"... ??? Please, enlighten me!

I have had a debate with one of my friends about this little game:  "1 rabbit saw 9 elephants while going to the river. Every elephant saw 3 monkeys going to the river. Each monkey had 1 tortoise in each hand. How many animals are going to the river?"  Answers:   4 - if you could rabbit and monkeys (which are described as "going to" the river)  10 - if you are counting tortoises in monkeys' hands 19 - if you assume all   my argument is that the tortoises are not "going to", but are being either "taken to" or "move towards" river. That's what I would say if someone holds me and goes to the river.  my friend's argument is that because they move towards the river, they are "going to" the river. he gave example of me being in the car.  Me: If I don't intend to go there, I'm being "taken to", even if in the car.  Question: does "going to" implies intent of the subject ?


I have   HOSTNAMEA,HOSTNAMEB,HOSTNAMEC,...   I have a third party workflow tool that can do the looping but can only use regex to parse values. I'd like to get a regex that grabs each hostname and puts into it's own variable in my workflow tool so the results will be  HOSTNAMEA HOSTNAMEB HOSTNAMEC ...   I'm struggling to get a regex that just grabs the text block X between the commas

I don't really understand regular expressions.  Can you explain them to me in an easy-to-follow manner?  If there are any online tools or books, could you also link to them?


(Descriptions are inside the code samples)  Take a look at this code  Public Sub Show()     System.Console.WriteLine("Hello")   ' Comment here will fail subsequencing syntax highlighting     System.Console.WriteLine("This should not be rendered as a comment") End Sub   Compare to this one  Public Sub Show()     System.Console.WriteLine("Hello")   ' Ending quote solve the problem for now --> '     System.Console.WriteLine("This is not rendered as a comment")     System.Console.WriteLine("Ending quote solve the problem for now") End Sub

I noticed that sometimes my code gets highlighted in different colors when rendered.   What is syntax highlighting? How does it work? Why isn't my code being highlighted correctly? How do I report a bug or request a new language? How do I use syntax highlighting? What languages are currently available on Stack Exchange?


I has an error if players use ShopGUI+ Plugin to buy or sell, it will error in consoler!  Plugin ShopGUI+:   Error console:  Please help me. Thanks!   class: package com.andrewyunt.townygui.listeners;    import com.andrewyunt.townygui.Menu;  import com.andrewyunt.townygui.TownyGUI;  import com.andrewyunt.townygui.utilities.CommandBuilder;  import com.gmail.filoghost.hiddenstring.HiddenStringUtils;  import org.bukkit.command.CommandSender;  import org.bukkit.entity.Player;  import org.bukkit.event.EventHandler;  import org.bukkit.event.Listener;  import org.bukkit.event.inventory.InventoryClickEvent;  import org.bukkit.inventory.ItemStack;  import org.bukkit.inventory.meta.ItemMeta;    import java.util.List;  import java.util.Set;     public class InventoryListener implements Listener {  @EventHandler public void onInventoryClick(InventoryClickEvent sukien) {      ItemStack item = sukien.getCurrentItem();      Player player = (Player) sukien.getWhoClicked();      if(!(sukien.getInventory().getHolder() == null))         return;      if(item == null || !item.hasItemMeta())         return;      ItemMeta meta = item.getItemMeta();     List<String> lore = meta.getLore();      if(!HiddenStringUtils.hasHiddenString(lore.get(0)))         return;      String action = HiddenStringUtils.extractHiddenString(lore.get(0));      boolean command;      command = action.startsWith("/");      if(!command)         new Menu(player, action);     else {         player.closeInventory();          Set<String> arguments;         try {             arguments = TownyGUI.plugin.commandConfig.getConfig().getConfigurationSection("commands."+ action + ".arguments").getKeys(false);         } catch(NullPointerException e) {             action = action.replace("/", "");             TownyGUI.plugin.server.dispatchCommand(player, action);             sukien.setCancelled(true);             return;         }          new CommandBuilder(arguments, action).beginConversation((CommandSender) player);     }      sukien.setCancelled(true); } }


I admit, I watch porn now and then on my android phone. But I never, ever, download something or click any adds or links. But here's the weird thing, sometimes when I visit such a website, an automatic download starts. I thought I removed them but when I installed an antivirus it detected 5 threats, all from that site. And the weirdest is, when I installed an other antivirus, it detected 4 more threats! Are these the same threats or did the first antivirus fail on me? And do android devices get severe viruses?

I use Linux for half a decade now, so I am not used to dealing with viruses anymore. To my surprise, I saw some discussion about antiviruses in Android. I haven't installed any yet, but this bugs me: are they really necessary? Are there (or were) any known viruses in the market? Doesn't Google runs an antivirus before allowing an app to the market?  I haven't had no problem in one year of Android, but my cellphone has a lot of important information, and I wouldn't like to be surprised with some virus cleaning my phone, or making international calls while I sleep, or whatsoever. Should I install an antivirus?


Usually, before going to sleep in night, we would say "Good night" to others but what to say when we are going to sleep for an hour or two during day time? It can be in morning or afternoon or evening.

It seems to be a silly question but I was puzzled when somebody bid me good night, when I was going to sleep at 1:00 PM. If somebody goes to sleep in the afternoon, is it correct to bid him "good night"? I think this is wrong.


How to transfer the following matrix into Smith normal form? $$\left[\begin{matrix} 2   & -2b & 0   \\ 0   &  2  & -2c \\ -2a &  0  & 2 \end{matrix}\right]$$ The final answer is $$\left[\begin{matrix} 2 & 0 & 0 \\ 0 & 2 & 0 \\ 0 & 0 & 2|abc-1| \end{matrix}\right]$$  But how we get it?

Let $A_R$ be the finitely generated abelian group, determined by the relation-matrix       $$R := \begin{bmatrix} -6 &  111  & -36 & 6\\ 5  &  -672 & 210 & 74\\ 0 & -255 & 81 & 24\\ -7  &   255       &-81 & -10 \end{bmatrix}$$       Reduce this matrix using Smith Normal Form and determine the isomorphism type of $A_R$.    I know that the Smith Normal Form of this matrix is:  $$\begin{bmatrix} 1 & 0 & 0 & 0 \\ 0 & 3 & 0 & 0 \\ 0 & 0 & 21 & 0 \\ 0 & 0 & 0 & 0  \end{bmatrix} $$  However, this was computed using Maple and I need to understand the method of computing this manually which I am struggling to grasp. Can anyone help?


I am wondering whether I should capitalize the first word after the colon in the following sentence:     I wondered: how can I utilize knowledge of algebra to reach my goals?   All resources on the internet I found dealt with different cases, such as enumerating after a colon. However, I am almost putting a different sentence after the colon.  I am aware I could rephrase the sentence not to include a colon, but I need to include it.

Should the first word after a colon be capitalized? Which of the following is correct?   For example: This. For example: this.


I use the code below to update the url link based on user text input:  <input type="text" id="q" /> <input type="button" id="submit" value="submit" />  <script> $(function () { $("#submit").click(function() {     var url = "/tag/";     url += $("#q").val();     window.location = url; }); }); </script>   Right now it works pretty fine when someone clicks the submit button. What I want is to make it also work when a user press the enter button.

I have one text input and one button (see below). How can I use JavaScript to trigger the button's click event when the Enter key is pressed inside the text box?  There is already a different submit button on my current page, so I can't simply make the button a submit button. And, I only want the Enter key to click this specific button if it is pressed from within this one text box, nothing else.  <input type="text" id="txtSearch" /> <input type="button" id="btnSearch" value="Search" onclick="doSomething();" />


I'm creating a simple console application in python and I'd like to replicate the shell functionally where pressing the up or down key lets you cycle through previous commands.   I can easily store a list of previous commands but the hard part is catching up and down key presses. I have read that you can do this using a ui library like Qt but this seems overkill for such a simple thing.  Does anybody know of a lightweight and simple way to do this that uses no non standard modules?

Is there a way of reading one single character from the user input? For instance, they press one key at the terminal and it is returned (sort of like getch()). I know there's a function in Windows for it, but I'd like something that is cross-platform.


Just recently installed Ubuntu 20.04.1 LTS replacing entirely Windows 10. I set up everything the way I wanted and I also installed Timeshift and made a backup successfully. I tried to go into Timeshift today and it requested my password to login, so I put the one and only password I have, which is the same password I log into Ubuntu with. The password is not accepted. I assumed it was because I wasn't a root user so I tried to become one using sudo -i and sudo -s (I read that ) and I got a Password prompt and here, again, I inputted the one and only password I have which is the same one I use to log into Ubuntu. That's when I got the message "user is not in the sudoers file. this incident will be reported". So I investigated the problem and tried this link . All seemed to have gone well with no problems or errors and I've also found the same information in multiple websites but the problem still persists. Does anybody have any ideas as to what else I can try? I don't care about being root in general, I just want to be able to open my apps like Timeshift and my Firewall app. Any help much appreciated. Note: I am entirely new to Ubuntu so forgive me if I haven't performed some basic actions. Also, the website brings  question as suggested but does not help my situation. Most questions I came across containing the specific error message are solved by running some simple commands such as sudo -i and sudo -s but in my case that approach is not sufficient.

After I add a user using adduser, I can't see it via System > Administration > Users and Groups unless I log out and then log in again. Is that normal?  Also, can I set a newly added user as a sudoer or do I have to change that only after adding it? How can I do that via the shell?  Finally, can I delete the original user that was created upon initial installation of Ubuntu, or is this user somehow 'special'?


I have a raster (25X25 meter) and I will make a new raster where each cell get the value of the sum of all the raster cells in a radius of 500m. I use QGIS. What is the best option to do this?

I'm attempting to use QGIS v2.0.1 to accomplish the same tasks that I can do using ArcMap v10.1 and I'm running into some trouble finding equivalent tools. In ArcMap I am using the Focal Statistics (mean) Spatial Analyst tool and I do not know if GRASS or SAGA has an equivalent in QGIS.   Does anyone know what the tool would be called if it exists?


I have a series of (x1,y1) points how to get back a series of (x2,y2) points that are on a Gaussian curve that has been fit to the data.

I have a series of (x1,y1) points.  I'm using a 3rd party software tool to which I feed these points. The tool then provides a mechanism for me to get back a series of (x2,y2) points that are on a Gaussian curve that has been fit to the data.  I'd like to confirm that the points I'm getting back are correct (because, frankly, sometimes they don't look like they are.)  What would be an easy on-line or Excel procedure that would allow me to enter the X1, Y1 series and then get back a series of X2, Y2 points, plot both series, and maybe even see the s.d.?  It's been 20+ years since I did any stats, so I'm just "cook-booking" this with no understanding of what I'm trying to do.  EDIT  The is a plot by wavelength, of intensity.  X-axis is the colors of a rainbow, in the familiar ROYGBIV order. The Y-axis is measured intensity of that particular color.   The help page from the vendor is here:    I call the library with each x1, y1 data point.  I then call the method above. I then call the library again with a series of x values (or maybe the x1 series itself), retrieving the y2 values on the fitted curve. I also retrieve the sd of the fit.  EDIT 2  Below is a link to an image of the dataset and Gaussian fit that has me concerned.  I think that the peak of the fitted curve is too low.


Today i posted one question . After some time i got three up vote on that question . But view count was 2 only  SO how it possible .  I also try to refresh page many time . Event see same link on different system its show me same thing .     and look at screen shot below .

How can a post be viewed 7 times and downvoted 8 times? Is it a bug?


I am using the subfigure environment provided by the subcaption package by Axel Sommerfeldt. Although reading the manual, I do not find a solution.  I would like to vertical align subfigures although they have different sized subcaptions  \documentclass[a4paper,oneside,10pt]{scrartcl}  \usepackage{graphicx} \usepackage{caption} \usepackage{subcaption}  \begin{document}  \begin{figure} \centering \begin{subfigure}[b]{0.3\textwidth}         \centering         {\rule{3cm}{2cm}}         \caption{Small subcaption.} \end{subfigure}% \begin{subfigure}[b]{0.3\textwidth}         \centering         {\rule{3cm}{2cm}}         \caption{Super super super super super super super super super super super super super super super super super super super large subcaption.} \end{subfigure} \caption{Cool (left) and uncool (right) pictures.} \end{figure}  \end{document}   not desired output    desired output    thx Benjamin

I'm using the subcaptionpackage to have figures side-by-side. The problem is that the package aligns the figures to their subcaptions (should I be taking a hint for the package name?) rather than the top of the pictures.   How can I algin the subfigures by the top border?  MWE:  \begin{figure}[h] \begin{subfigure}[b]{.5\linewidth} \centering\large A \caption{A subfigure}\label{fig:1a} \end{subfigure}% \begin{subfigure}[b]{.5\linewidth} \centering\large B \caption{Another subfigure with a long, long, long, long caption.}\label{fig:1b} \end{subfigure} \caption{A figure}\label{fig:1} \end{figure}   Result:


Do anyone know how I can copy information via href to clipboard? I'm going for something like this;  <?php  print "Number: " . $number . "";  ?>   When something click the link the information given in $number should be copied.   Thanks!

What is the best way to copy text to the clipboard (multi-browser)? I have tried: function copyToClipboard(text) {     if (window.clipboardData) { // Internet Explorer         window.clipboardData.setData("Text", text);     } else {         unsafeWindow.netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");         const clipboardHelper = Components.classes["@mozilla.org/widget/clipboardhelper;1"].getService(Components.interfaces.nsIClipboardHelper);         clipboardHelper.copyString(text);     } }  But in Internet Explorer it gives a syntax error. In Firefox, it says unsafeWindow is not defined. A nice trick without using :


I am using jquery for dynamic content/page loading.  I have a basic nav with links (for SEO purposes) and this code to check for click events and to make sure the new 'page' is browseable with history:    $("nav a").on("click", function ()     {         let _href = $(this).attr('href');           history.pushState(null, null, _href);         loadContent(_href);          $('.activePage').removeClass('activePage');         console.log($('.activePage'));           return false;     });      function loadContent(href)     {          let page = $("#pageWrapper");          page.fadeOut(200, function ()         {             page.hide().load(href + " #pageWrapper", function ()             {                 page.fadeIn(200);             });         });      }     });   My problem is that when I click my nav links sometimes it loads with jquery like I want it to but other times it still links it as if I were to click a normal  element, despite return false...

I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off.  This happens on page ready and works just fine.  The problem I have is that any select boxes I add via Ajax or DOM after the initial loop won't have the event bound.  I have found this plugin (), but before I add another 5k to my pages with a plugin, I want to see if anyone knows a way to do this, either with jQuery directly or by another option.


I've tried to install Anbox using , with a minimal distribution 18.04, without a desktop.   I had hoped that the required packages that are needed to create a window will be installed all along. I don't know how far off I am with that. When I try to open the anbox.appmgr the the following error comes up:  realpath: '': No such file or directory  realpath: '': No such file or directory  realpath: '': No such file or directory  realpath: '': No such file or directory  realpath: '': No such file or directory  realpath: '': No such file or directory  realpath: '': No such file or directory  realpath: '': No such file or directory  [2020-05-03 13:33:50] [daemon.cpp:61@Run] Failed to connect to DBus   Has anyone an idea what to do?  Thanks a lot

I'm trying to install Anbox in my new Ubuntu 16.04 using instructions from  . It seemed to work, but I got no icon in my dash, so I suspect that the installation is not complete. With Synaptic  Package Manager I can see that anbox-common & anbox-modules-dkms are installed, but I have no icon in my dash, so I tried running   sudo snap install --edge --devmode anbox   and got this error:  error: cannot install "anbox": Get    https://search.apps.ubuntu.com/api/v1/snaps/details/core?channel=stable&fields=anon_download_url%2Carchitecture%2Cchannel%2Cdownload_sha3_384%2Csummary%2Cdescription%2Cdeltas%2Cbinary_filesize%2Cdownload_url%2Cepoch%2Cicon_url%2Clast_updated%2Cpackage_name%2Cprices%2Cpublisher%2Cratings_average%2Crevision%2Cscreenshot_urls%2Csnap_id%2Csupport_url%2Ccontact%2Ctitle%2Ccontent%2Cversion%2Corigin%2Cdeveloper_id%2Cprivate%2Cconfinement%2Cchannel_maps_list:    dial tcp: lookup search.apps.ubuntu.com on [::1]:53: read udp    [::1]:54255->[::1]:53: read: connection refused   What am I doing wrong? Why was the connection refused? According to the instructions, it seems this is the correct command to install it.  ps: I'm not that familiar with Linux, I'm more of a Windows guy, trying to learn Linux.


I'm connected to a server through ssh and want to run a process that will take a long time. I connect to the server by using ssh in my laptops terminal, but I want to be able to turn my laptop off but still have the progress running on the server. Since they're two separate computers, it seems like I should be able to do this, but I'm not sure if it's possible through ssh.

I sometimes have long running processes that I want to kick off before going home, so I create a SSH session to the server to start the process, but then I want to close my laptop and go home and later, after dinner, I want to check on the process that I started before leaving work. How can I do that with SSH? My understanding is that if you break your SSH connection you will also break your login session on the server, therefore killing the long running process.


I have written a book and inserted a lot of illustrations. All illustrations are input in my document as:  \begin{center} \includegraphics [scale=1]{image/1_12.pdf} \end{center}   I have about 500 images/illustrations  I would like to have the list of all inserted images/illustration, something like:  1_12.pdf  1_23.pdf  test.pdf  and so on. Is it possible to do that? Thanks a lot for the answer.

I have a TeX document that is embedding a huge amount of figures from a fig folder that is full of another humongous amount of other figures.  I would like to move the document along with its figures, but I don't want to take the whole fig folder, just the figures in there that are embedded by the document.  Is there a package (or any other way) that allows me to, for example, print out the filenames of all the figures embedded by the document? Something like:  fig/figurename1.eps fig/figurename2.eps ... etc   I could then just copy-paste that list and add some cp's in a plain text file and automate the copy of those files to my desired location by running the file in my shell:  $ cp fig/figurename1.eps wherever/fig/ $ cp fig/figurename2.eps wherever/fig/ ... etc   Of course this is just an idea, if somebody has an alternative to the "file listing and copy-pasting in a shell file" I would be happy to listen =)


My system is Ubuntu 20.04.2 LTS, Gnome version is 3.36.8. I am going to Settings -> Keyboard Shortcuts. Some keyboard shotcuts can be changed, while some are not.eg; "Switch to next input source" (for language switching). I press it, the pop up window says "Set Shotcut". If I press e. g. Alt+Tab, the system allows me to do that. However if I want to do Alt+Shift (which is the classic one for language switching), the system does nothing.. Neither works Ctrl+Shift, Ctrl+Alt etc. As far as I see, Alt+Shift is not assigned to any other other command. Please help..

Can I use Ctrl+Shift for changing languages? I can't set this hotkey for changing keyboard languages.  At this moment Alt+Shift switch languages, but I can't see this hotkey in keyboard hotkeys list or in   gsettings list-recursively  org.gnome.desktop.wm.keybindings | sort | more   output.


I'm wondering how I would go about evaluating the definitions of a python file in the directory my IPython REPL is running in. This would seem like a great workflow to be able to test the functions I just wrote inside the REPL.  This doesn't work:  with open('file.py') as f: eval(f.read())

It seems they canceled in Python 3 all the easy way to quickly load a script by removing execfile()   Is there an obvious alternative I'm missing?


I have an  with Windows 8 installed from the factory and recently upgraded to .   I have dual booted Windows and Ubuntu on my last Windows 7 laptop, but now I can´t figure it out. On my last laptop I would power it up, press F12 or something and boot it trough the USB drive, and then install trough the option Install ubuntu side-by-side Windows or would just install it on other partition. And it would work just fine.  Now, with Windows 8.1 I don't get that initial boot screen that tells me to press F12 to boot from another device; the computer just starts booting really quick (xD). I have to go to settings and select advanced boot and tell it to boot from USB. And when I get to install Ubuntu it doesn´t show the option to install side-by-side with Windows.  I hear some talk about , but I don´t know what that is.  Can someone please give me a hand?

I'm absolutely new to Linux. I would like to know how to install Ubuntu alongside the pre-installed Windows 8+ OS.  Should I do it with Wubi, or through the Live USB/DVD?  What steps do I need to take to correctly install Ubuntu?


For instance, is it grammatical?     I looked from the window and spotted a person. It crossed the street.

Is there a pronoun I can use as a gender-neutral pronoun when referring back to a singular noun phrase?  Each student should save his questions until the end. Each student should save her questions until the end.


i've commented an answer on SO, but now i could not find the Question/Answer again. Is there a way, to see all my comments for finding the SO-Page?  Thank you

I suggested this on UserVoice, but with the discontinuation of that site wanted to move the suggestion and discussion here.  A list of all comments on the User Tab would be useful. Recent comments are available from the recent tab but I'd like to have access to all comments. I would envision something very close to the list of Answers already present on the profile page.


Every single time I open File Explorer or switch to a File Explorer window, it first paints several frames of the white background before it paints the actual, dark background. This appears to the naked eye as a very sharp, annoying "flash" effect. If you experience this 56 billion times a day, it slowly drives you insane... And it's driven me insane. I cannot express in words how much this bothers me, especially since this is a new computer whose entire "new computer" phase has been ruined by this.  The same thing happens for cmd.exe windows, but NOT for Firefox, Notepad++, or even Microsoft's own "Calculator". It seems to basically happen only with File Explorer and cmd.exe. And out of those two, only the File Explorer one truly bothers.  What could be causing it? How do I fix it? I've searched so long and hard but find absolutely nothing. Not a single mention of anyone else having this, much less how to solve it.  Please note that, even though it obviously is not due to the graphics drivers (since only specific programs have this issue), I have NUMEROUS times tried uninstalling the GPU drivers, rebooted, installed the new ones (and even old/stable ones), both from HP's site and NVIDIA's. I have made extremely sure that they are the correct ones. I have tried various random "tricks" suggested, but nothing has solved this whatsoever.  It's as if this bug is part of Windows 10. winver.exe says "1903". I did not have that version of Windows 10 on the previous computer, where I did not have this issue. So maybe it's somehow related to version 1903 of Windows 10?  Either way, the damage has already been done. I can never like this computer after it has put me through this torture. Still, a solution would be highly appreciated to save what's left of my sanity.  PS: "Not using dark theme" is not an option. My eyes die even quicker if I enable that bright, glowing theme.

The latest version of Windows 10 (1809) has added a new feature to Windows Explorer (and various win32 programs). Specifically, if one uses the Dark Theme for UWX apps, the Windows Explorer also turns dark.   Here's an example of how an UWX app looks after enabling the Dark Theme:     Here's an example of how the Windows Explorer looks after enabling the Dark Theme:     However, while I enjoy the dark theme for UWX apps, I prefer using the light theme for Windows Explorer (and other win32 programs).   Question: Is there an option or a "hack" that allows me to use the dark theme for UWX apps, but the light theme for Windows Explorer (and possibly other win32 programs)?


I remember hearing two words, each describing a relationship to scope, or a containing set. I think they are prefixed with micro- and macro-, but am not certain (I'll call them 1 and 2).    1 describes a type of thing which, by definition, is contained within the definition of 2.  2 describes a type of thing which, by definition, contains 1.    For example, a square is a 1 of a rectangle. A rectangle is a 2 of a square. An iPhone is a 1 of a computer, and a laptop is also a 1 of a computer.  I hope that makes enough sense. This is difficult to describe because it is so conceptual in nature.

Any given square is always a rectangle, but a rectangle isn't necessarily a square, so squares and rectangles have a _ relationship. I've been noticing this sort of thing everywhere ever since I noticed that I didn't know a good word for it. I've been calling it a container relationship because one class of things is contained within a larger class of things. However, a "container" relationship doesn't sound very good and doesn't really convey the meaning on its own. A more elegant word would be helpful.  Edit: A specific definition would be something like: a is always b. b is sometimes a.


I hope this isn't to broad, but I am wondering if the following can be done somehow?  Lets say I have a Nuget-package for Project A and a solution with some projects (Project B, Project C). Now, Project C references Project B. It also has a Nuget-Dependency for Project A (which was developed within a different solution).  When I compile Project C, I get the dll of Project C along with the dll for Project A. Is there a way, the dependencies can be compiled into the dll for Project C, so that i only have one dll which conatains all its dependencies as well as the actual project?  The Reason is that I want to load ProjectC.dll at runtime in a different solution. But when i do so, the dependencies are missing.  How would one usually handle that?

If you create a class library that uses things from other assemblies, is it possible to embed those other assemblies inside the class library as some kind of resource?  I.e. instead of having MyAssembly.dll, SomeAssembly1.dll and SomeAssembly2.dll sitting on the file system, those other two files get bundled in to MyAssembly.dll and are usable in its code.    I'm also a little confused about why .NET assemblies are .dll files. Didn't this format exist before .NET? Are all .NET assemblies DLLs, but not all DLLs are .NET assemblies? Why do they use the same file format and/or file extension?


Consider this example: \documentclass[margin=1cm]{standalone} \usepackage{tikz} \begin{document}  line1  line2  \begin{tikzpicture} \draw (0, 0) -- (2, 2); \end{tikzpicture} \end{document}  In the output everything is on one line:  How to have a new line in standalone?

I tried to combine this answer  with my answer  But the pdflatex -shell-escape table.tex ignores linebreaks and the 3 tables are horizontally aligned and not vertically. table.tex \documentclass[convert]{standalone} % \documentclass{article}  \usepackage{booktabs} % for nice lines \usepackage{siunitx}  % nice numbers and units and 'S' in table \usepackage{multirow} % enable \multirow command  \begin{document} short answer to your question:\\ \begin{tabular}{|c|c|S|} \hline Genre & Name & {Weight}\\\hline Humain & Aragorn & 102 \\\hline \multirow{4}{*}{Hobbit}&Frodon & 32.1\\\cline{2-3}     &Sam & 3.2 \\\cline{2-3}     &Peregrin & 2.232\\\cline{2-3}     &Meriadoc & 23 \\\hline Elfe&Legolas & 34.5 \\\hline \end{tabular}\\[1cm]   You can also use the power of booktabs and siunitx:\\ \begin{tabular}[ht]{l c S} % alignment l = left, c = centre, S = at decimal - needs siunitx \toprule Genre&Name& {Weight}\\  % protect non numbers with {} in S columns \midrule Elfe&Legolas & 34.5\\ Dwarf&Peter & 103.31\\ \bottomrule \end{tabular}\\[1cm]  And combine that with your table:\\ \begin{tabular}{c c S} \toprule Genre & Name & {Weight}\\\midrule Humain & Aragorn & 102 \\\midrule \multirow{4}{*}{Hobbit}&Frodon & 32.1\\\cline{2-3}     &Sam & 3.2 \\\cline{2-3}     &Peregrin & 2.232\\\cline{2-3}     &Meriadoc & 23 \\\midrule Elfe&Legolas & 34.5 \\ \bottomrule \end{tabular}   \end{document}


An integer $n$ is randomly chosen from $1$ to $k^2$, where $k$ is an integer. What is the probability that $n$ is a perfect square?  I know I have to first figure out the probability of getting a perfect square and then take the complement of this.  How would I go about? Thank you!!

Consider $\sqrt{n}$, where $n$ is an integer and $1\le n \le 10$. How many of these ten numbers are irrational?        An integer $n$ is randomly chosen from $1$ to $k^2$, where $k$ is an integer. What is the probability that $n$ is a perfect square?   For the first one I had figured out it was $7$ irrationals numbers but did not know how to prove the second question


Recently having few observation stack exchange site , I noticed that hot question is high voted. When question is said to be hot question all the user sees it first or user sees that question before any other and if question is good and worthy to be a hot question it is high voted and views are too high. Is it so?  So if ask a question  and I get too many votes in less time does my question becomes a hot question  in that site ?

Right now  is fairly broken -- it's a simple descending sort by views. As Joel said , it is "a self-fulfilling prophecy." But this is not intentional, it's only because we haven't had time to improve it yet! As I sit down to write a better algorithm, I thought you guys might have some insight into what would make a good formula to determine the "hot" questions -- over the last 24 hours, the last week, the last month, and all time. Here are the variables we have to work with:  Votes [aka Score] Views Answers Answer Votes [aka Score] Whether the question has an accepted answer or not Time question was originally asked Time of last activity on question Reputation of asker Reputation(s) of answerers  Joel cited the reddit formula as an example, but I think our site is a little different than just a basic link submission site. Plus, we have more variables and data to work with. I found a  describing a few formulas: Y Combinator Hacker News  (p - 1) / (t + 2)^1.5 p = votes (points) from users t = time since submission in hours  Reddit  t = (time of entry post) - (Dec 8, 2005) x = upvotes - downvotes y = {1 if x > 0, 0 if x = 0, -1 if x < 0) z = {1 if x < 0, otherwise x} log(z) + (y * t)/45000  Thoughts? Ideas? I don't want to overthink this; I just want the "hot" questions to be relevant and useful to us. So the simpler the algorithm the better! Based on my analysis of the above and the comments so far, here's the second version of what I have implemented so far. This might suck. I don't know:  (log(Qviews)*4) + ((Qanswers * Qscore)/5) + sum(Ascores) -------------------------------------------------------- ((QageInHours+1) - ((QageInHours - Qupdated)/2)) ^ 1.5  Note that accepted answers weight not at all in hotness. This is intentional, as I feel accepted answers are a fine social contract, but not a good data point for question or answer quality. This algorithm will heavily favor questions with LOTS of answers, as the sum(Ascores) are now included -- one assumes if there are lots of answers, there will be a lot more voting on the answers, too. Update: Note that this formula is what is used on the  linked from the homepage of each site. It is not the formula used to determine the  list. See .


I have the following code trying to calculate how much time it takes in milliseconds to build a docker container. However I am facing syntax error and command not found issue, running bash script bash pipeline.sh #!/bin/bash echo 'Initiating pipeline' cd /home/switch-approach/server-c start=date+'%s%3N' sudo docker build -t server-c . end=date+'%s%3N' echo "duration: $((duration=end-start)) seconds."  Retrieving error date+'%s%3N' command not found  operand expected syntax error start

I want to assign the result of an expression (i.e., the output from a command) to a variable and then manipulate it – for example, concatenate it with a string, then echo it.  Here's what I've got: #!/bin/bash cd ~/Desktop; thefile= ls -t -U | grep -m 1 "Screen Shot"; echo "Most recent screenshot is: "$thefile;  But that outputs: Screen Shot 2011-07-03 at 1.55.43 PM.png Most recent screenshot is:   So, it looks like that isn't getting assigned to $thefile, and is being printed as it's executed. What am I missing?


I saw a friend make lightning come out of dispensers or they made it seem like it came out of dispensers. I know they used a command block.   How can I summon a lightning like that?

For a little things I'm doing I need to make charged creepers. However, finding one in the wild is almost impossible and I need to have people see the creepers change into charged creepers, therefore using /summon to summon a charged creeper won't work. Is there a command to summon lightning?


I want a blank mysql password on my new Ubuntu 16.04 development machine the same as I've had on previous machines.  It plays well with my existing local ruby on rails apps configuration files which use root.  I start with  sudo apt-get install mysql   then I can use   service mysql start   and when I use   ps aug | grep mysql   I see the process running  mysql    24618  6.5  1.6 1230276 133536 ?      Ssl  19:03   0:00 /usr/sbin/mysqld   I stop it with  service mysql stop   and then I use   sudo mysqld_safe --skip-grant-tables   and in another window I do  mysql>  mysql> UPDATE mysql.user SET authentication_string = ''     -> WHERE User = 'root' AND Host = 'localhost'; Query OK, 1 row affected (0.00 sec) Rows matched: 1  Changed: 1  Warnings: 0  mysql> FLUSH PRIVILEGES; Query OK, 0 rows affected (0.00 sec)   I then use   sudo kill -9 [pid_of_mysqld_safe]   and then  service mysql start   to start it normally but when I try  mysql -u root   I get  ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)   I also tried using an actual string instead of '' for the password but still had the same issue  I've gone through   and  and  and   but they haven't helped, I get the same error.  $ sudo systemctl status mysql   shows  ● mysql.service - MySQL Community Server    Loaded: loaded (/lib/systemd/system/mysql.service; enabled; vendor preset: enabled)    Active: active (running) since Wed 2016-08-24 20:04:49 EDT; 4min 39s ago   Process: 9018 ExecStartPost=/usr/share/mysql/mysql-systemd-start post (code=exited, status=0/SUCCESS)   Process: 9013 ExecStartPre=/usr/share/mysql/mysql-systemd-start pre (code=exited, status=0/SUCCESS)  Main PID: 9017 (mysqld)    CGroup: /system.slice/mysql.service            └─9017 /usr/sbin/mysqld  Aug 24 20:04:48 Ubuntu2016 systemd[1]: Starting MySQL Community Server... Aug 24 20:04:49 Ubuntu2016 systemd[1]: Started MySQL Community Server.

I've set up mysql and phpmyadmin and chose not to set a password when installing hoping that once set up i could login with root and no password but i get the following error from phpmyadmin:  Login without a password is forbidden by configuration (see AllowNoPassword)   I have previously moved the phpmyadmin folder to /var/www/   I have tried changing the following line  $cfg['Servers'][$i]['AllowNoPassword'] = false;   to  $cfg['Servers'][$i]['AllowNoPassword'] = true;   but still had no success, so i am wondering is there a way i can change the root passwords for both so i can access phpmyadmin and create databases.


For example:     Detective Jones   I think the D in Detective Jones should always be capitalized, because I believe that is the norm.  But what if, after introducing Detective Jones, I later refer to him as The Detective. For example:     Detective Jones asked me a few question, which I answered. After   listening carefully and taking notes, the Detective then came back to   me with some more questions.   I think you would capitalize the D, because "the Detective" is being used as a shorthand for "Detective Jones". But it looks a little odd, so I am not sure.

Would you capitalize the job title in the following sentence?      I am writing this letter in regard to Joe Brown who is applying for the director of teaching and learning position in the XYZ School District.


For example:  def test(a)    a = 2    b = 5+a    x = a*2    return x   Is there a way to call the variable 'b' outside of the function?

How can I create or use a global variable in a function?  If I create a global variable in one function, how can I use that global variable in another function? Do I need to store the global variable in a local variable of the function which needs its access?


Why is the infinite sphere contractible?  I know a proof from Hatcher p. 88, but I don't understand how this is possible. I really understand the statement and the proof, but in my imagination this is weird.  Thanks for your help.

Let $\mathcal{T}_{\infty}= \left\{ U \subset \mathbb{R}^{\infty}: \ U \cap \mathbb{R}^n \in \mathcal{T}_n, \text{ for } n=1,2,... \right\} $. Of course $\mathcal{T}_{\infty}$ is topology in $\mathbb{R}^{\infty}$. How to prove that $S^{\infty} = \{ v \in \mathbb{R}^{\infty} : \ \|v\|=1 \}$ is contractible?   :)  Can we find homeomorphism without fixed point from $D^{\infty} = \{ v \in \mathbb{R}^{\infty} : \ \|v\| \le 1 \}$ onto $D^{\infty}$? I was trying to find such homeomorphism, but I failed...


The strip uses .5-2A and 5 volts. I'm using four AA batteries, so the voltage becomes 6. What do I do to reduce the voltage, and get the right current? Will the strip itself just draw the current in it's own way since it's remote controlled? I read online something that said something like the equation for the extra volts is you take the original volts, and subtract it by the end voltage you want. Then you take the difference and put it in a ratio to the end voltage. Like 6-5=1. 1:5, meaning you use two resistors, the second of which being 5 times the first resistor. Is that correct? And if so, what about the current?  Edit: What if I used 4 rechargeable AA batteries. Each is like 1.2 volts, 4 of them would make 4.8 volts. Online it says that the internal resistance is about 30mΩ-100mΩ. That means .03Ω-.1Ω right? Using ohms law to find the current, V/R=I, and the max resistance, that should be 1.2/.1=12. So a single rechargeable AA battery can pump out 12 amps? Correct me if I'm wrong

When would you use a voltage regulator vs a resistor voltage divider?  Are there any uses for which a resistor divider is particularly bad?


I tried to solve this problem like:  Remainder of $3^2 / 7$ is $2$  Remainder of $3^3 / 7$ is $-1$  Then i square that, and I get  Remainder of $3^6 / 7$ is $1$  Then I can go all the way to:  Remainder of $3^{2016} / 7$ is $1$  Now how do I get to 2020? Or is there another way to solve this problem?

I've read about Fermat's little theorem and generally how congruence works. But I can't figure out how to work out these two:   $13^{100} \bmod 7$ $7^{100} \bmod 13$   I've also heard of this formula:  $$a \equiv b\pmod n \Rightarrow a^k \equiv b^k \pmod n $$  But I don't see how exactly to use that here, because from $13^1 \bmod 7$ I get 6, and $13^2 \bmod 7$ is 1. I'm unclear as to which one to raise to the kth power here (I'm assuming k = 100?)  Any hints or pointers in the right direction would be great.


Are  Pass the files to the concerned person   and   Pass the files to the person concerned   the same?  I was told the first one means "worried person."

Adjectives are placed before nouns. But sometimes I've seen (though I'm not sure if they are correct), things like:     The item placed there   I know that it may be a short way of saying "The item which is placed there".    Is the past participle "placed" considered as an adjective in that sentence? Can any past participle used in this way by ommiting the relative pronoun+subject of the relative clause? Is there any exception for the rule that adjectives must be placed before noun?


I'm trying to do a different sql statement in case that the user submit the search form. I'm trying with this code below, but I'm getting an error and I'm not understanding why, because the code seems gode for me.   Do you see here something that can be the cause of these errors?  Errors Im getting:     Call to a member function bindParam() on a non-object in $readNews->bindParam        Notice: Undefined variable: readNews in $readNews->bindParam(':begin', begin, PDO::PARAM_INT);        Fatal error: Call to a member function bindParam() on a non-object in   F:\Xampp\htdocs\projeto\admin\posts\noticias.php on line 53   My code:  $pag = (empty($_GET['pag']) ? '1' : $_GET['pag']); $maximo = 5;  $begin = ($pag * $max) - $max;     if (isset($_POST['search']))  { $search = $_POST['search']; if(!empty($search) && $search != 'Title:') { $readNews = $pdo->prepare("SELECT * FROM news WHERE title LIKE CONCAT('%', :search, '%') ORDER BY data DESC LIMIT :begin, :max"); $readNews->bindParam(':search', $search); } }        else { $readNews = $pdo->prepare('SELECT * FROM news ORDER BY data DESC LIMIT :begin, :max'); }  $readNews->bindParam(':begin', begin, PDO::PARAM_INT); $readNews->bindParam(':max', $max, PDO::PARAM_INT); $readNews->execute(); $resultReadNews = $readNews->rowCount();

So I'm refactoring my code to implement more OOP.  I set up a class to hold page attributes.  class PageAtrributes  {   private $db_connection;   private $page_title;      public function __construct($db_connection)      {         $this->db_connection = $db_connection;         $this->page_title = '';     }      public function get_page_title()     {         return $this->page_title;     }      public function set_page_title($page_title)     {         $this->page_title = $page_title;     } }   Later on I call the set_page_title() function like so  function page_properties($objPortal) {         $objPage->set_page_title($myrow['title']); }   When I do I receive the error message:     Call to a member function set_page_title() on a non-object   So what am I missing?


WinUSB keeps on freezing. Unetbootin doesn't work, and neither does Tuxboot. I'm running Ubuntu 12.04.

I need to create a Windows installation USB drive from an ISO file. I used UNetbootin which seems to be the only tool that can write non-Linux images.  The USB disk boots (sort of), but it gets stuck at the very first stage. A UNetbootin splash screen appears that keeps counting down from 10 to 0, and then restarts.   The screen looks like this:    Is there a way to make Windows boot from a USB image created on Linux?


EDIT: this is NOT a duplicate of .  That question is about someone who's computer came with XP, mine came with Windows 7.   I intend to sell an old laptop that came with Windows 7 installed.  I don't have install disks.  If I follow the instructions here (for a factory reset):   Will this be sufficient to guarantee nobody can access any private data I have on the machine?    And will I have to worry about DRM stuff at all?  They mention it here:   If it is more complicated than just following the steps in the first link, what else do I need to do?

I have a laptop that came with Windows XP. I upgraded to Windows 7 when it came out, and am planning on selling the laptop. Unfortunately, I think the Windows 7 upgrade disc got accidentally thrown out when I was throwing some old software out.  I was planning on doing "Darik's Book and Nuke" to wipe everything, but then I would have no way to get Windows 7 back on it legally. Is there any way I can restore Windows 7 to a clean install, and then "wipe unused space" with a disk utility to protect my information?  I do have the Windows XP factory restore disc that came with the laptop, but it will obviously sell easier and probably for more with Windows 7 on it.  Any suggestions? Thank you.


Firstly, I apologise, I know this gets asked a lot and I've read through other answers, but I'm still not getting it. As far as I can tell I've done everything right. Can anyone see what's missing? That's a model of a moa that I'm trying to drop into a short film, but at this stage I'm just working with a still for the sake of colour matching. Basically, I hit "render" and just get the bird without the background... like I said in the title, I'm brand new to Blender so it's probably something fundamental.  Thanks in advance.

First time I've used cycles rendering engine.  I'm using a movie clip as the background in short animation. Selected RBGA under Property Tab, and Transparent under Film Tab.  It looks good and individual frames in OpenGL active viewport render, and looks fine.  When I try to get it to spit out PNG files of the finished animation the objects render out fine, except no movie clip background as Blender Render engine did when using Paper Sky setting.  Operator error, or am I trying to do something Cycles won't do?  Haven't found an answer in my searches so far.  Can anyone point me in the right direction please.   Addition:  I think I found my problem after a couple more hours of research.  Post should read "operator ignorance" instead of operator error.  Too tired to try the solution tonight, everything looks better in the morning. Thanks anyway.  Sorry, I just saw your posts.  Really tired.  Much appreciation.


My question is exactly the same as TTome! ()  "I've been trying to test the Viewshed analysis plugin on QGIS 2.10, but it keeps giving back error messages. I've tried to reduce the radius area and have also reprojected both my DEM and my point shapefile to UTM, in order to avoid a possible memory error mentioned in another question regarding this plugin (that the using of geographic coordinates might cause a memory error). Still, I keep getting Python error messages when I try to run it. Does anyone know whats going on? Is this plugin "broken"?"  Error message:


I died in my hardcore mode world that I really care about. and I changed myself to creative mode, grabbed my stuff, put it in a chest and made a new book explaining to my future self how I died and how long I survived for in case my future self curiously came into the world to see what it was.  After I finished writing the book I grabbed my book of coordinates from my chest that I created and wrote before I died. I decided to play around with the save toolbar hotkey (dumb idea) and went to try save my toolbar, but instead of pressing C+6 like I meant to, I accidentally pressed X+6, which cleared my inventory completely because toolbar number 6 in the inventory was already previously empty, so it essentially replaced all my items with air.   My question here is, is there any way I can find and recover those 2 books in the world files or game files? I don't care what it takes to get those books back even if I have to mod the game, I just want a way to recover the books.  I don't really care much for the death book, just as long as I can get my coordinates back because they are extremely important to have.

I used the /clear command, and I accidentally got rid of a very important book. Is there a way to get it back without having to rewrite it?


What is the main difference between df[:] and df[::] and could you please give me one sample example for regarding this.i was unable to understand.

I need a good explanation (references are a plus) on Python's slice notation.   To me, this notation needs a bit of picking up.   It looks extremely powerful, but I haven't quite got my head around it.


Someone told me that the term "moment" in Statistics comes from Physics. But I fail to understand how it relates to the definition of a moment of a force, which is a measure of its tendency to cause a body to rotate about a specific point or axis.  Update: I missed the  about moments and was about to delete mine but I didn't for the following reasons:   The accepted answer is very useful and helps me to better understand the analogy with Physics (and may help another OP).  The answer and the comments clarify the idea that the analogy is more about the moment of inertia than of a force.  The answer in the original question is more about the origin of the concept, which is also helpful. The title of my question is probably easier to understand for a non-native English speaker and may explain why I missed the original post (and which can also be missed by another OP).

I KNOW what moments are and how to calculate them and how to use the moment generating function for getting higher order moments. Yes, I know the math. Now that I need to get my statistics knowledge lubricated for work, I thought I might as well ask this question – it's been nagging me for about a few years and back in college no professor knew the answer or would just dismiss the question (honestly). So what does the word "moment" mean in this case? Why this choice of word? It doesn't sound intuitive to me (or I never heard it that way back in college :) Come to think of it I am equally curious with its usage in "moment of inertia" ;) but let's not focus on that for now. So what does a "moment" of a distribution mean and what does it seek to do and why THAT word! :) Why does any one care about moments? At this moment I am feeling otherwise about that moment ;) PS: Yes, I've probably asked a similar question on variance but I do value intuitive understanding over 'look in the book to find out' :)


When I use simulation to determine a p-value I am aware that the exactness of my p-value will be at most an estimate because I am using the scores of my sample and not my population, so that my computed p is on average close to its true p-value.   How do I deduce whether my estimate is a good estimate or a not-so-good estimate? Is there a some kind of rule?   My guess would be that it should be something like N ≥ 30 but I would appreciate an official answer.

The second paragraph of the  section of the Wikipedia article on resampling statistics, the values of a confidence interval for a p-value from a MC sampling is given:     After $N$ random permutations, it is possible to obtain a confidence interval for the p-value based on the Binomial distribution. For example, if after $N = 10000$ random permutations the p-value is estimated to be $\hat{p}=0.05$, then a 99% confidence interval for the true $p$ (the one that would result from trying all possible permutations) is $[0.044, 0.056]$.   What's the formula to calculate it?


I have a content type with 20 different fields.   Now the project requirement changed and I dont need 15 fields of them. So I removed all those unwanted 15fields from content type.   But the database is still holding all the 15 tables and also the revision table, Why? What happens if I remove it?  I feel like having these many unused tables in database might impact the performance. Will it really have impact on the performance?

I have created fields deleted them. Tables for the fields are gone upon deletion, but they are still in field_config and field_config_instance  Is there anyway to clean them?  Thanks


I understand that the galaxy has a synchronized form of keeping time. It's almost always referred to as standard time. A standard day, week, year etc. They would need that since a a day, week, or year will vary from planet to planet. So my question is, What is the Galactic Calendar Synced to?  I thought it might be the rotation of Courescant since it's the capital of the Republic and the Empire, but I'm not sure.  I would also like to know when the Galactic Calender was established.

I seem to remember several dating systems mainly in the Star Wars Expanded Universe. Furthermore, I was wondering if periods of time such as seconds, days, or months represent the same amount of time as they do in the real world.  So these are the main points of this question:   Which are the different dating systems (if there is indeed more than one) in the Star Wars galaxy? How are they related in regard to time offsets and such? (e.g. One system's year 5000 is another's year 268) An explanatory timeline graphic - perhaps including some important events - would be especially appreciated! Do amounts of time in the dating system(s) such as minutes or hours represent the same amount as in the real world? If more than one system exists, do the amounts of time carry over between them? (e.g. 1 minute is the same amount of time in all systems.) If the times carry over (or there is, in fact, only one system), what planet are the units of time based on? Coruscant?   Sorry if it seems I have asked too much in one question - splitting this question up into multiple questions did not appear to be a good idea as much of its content is very related.  Thanks for your time!


I'm a Vim user, and usually I just install vim via a one liner "apt-get install vim", but for red hat how can I update the 7.2 version to 7.4 with a one liner?  I googled it and many places tell me to compile my own vim 7.4, but i'm really not confident on how this works and where does it even get stored? what is the program files folder equivalent in redhat? why isn't there a one liner to just upgrade to vim 7.4 without having to compile stuff like this.

If there are two (or more) versions of a given RPM available in a YUM repository, how can I instruct yum to install the version I want?  Looking through the Koji build service I notice that there are several versions.


Is there a good SE site that is only about refactoring?  I know there are sites like this, but SO has the largest audience of programmers so a section where you can just post a code snippet and people can give advice on refactoring it.

There seems to be more than a few computer science/programming Stack Exchange networks (is that the correct term?). Stack Overflow, being the first, has by far the most users, questions, and answers.  What is the reasoning for creating the others, and are there clear guidelines for which kinds of questions should be posted? I can see a large amount of potential overflow, many cases of people not getting a good answer to their question, because the person who has the answer isn't browsing that particular network at the moment.  I understand that they were probably created for organizational purposes, but wouldn't it almost make more sense to just have them as categories under Stack Overflow, keep them separated but still connected, instead of making people have to create multiple 'account's, one for each network?  I am sure there was a very good reason to break them up, but as someone that is new to SE, it can be somewhat intimidating to decide which one to post in to ensure you get a good answer. For example, if I am a computer science student, my first instinct might to be to post in the computer science network, until I see that it literally has 1% of the users as the Stack Overflow network, which still seems to be for programming/computer science related questions.  So my second instinct would then to be to post it into the Stack Overflow site on the basis that I have a significantly higher chance of my question being seen and getting a good answer. Then I notice that there is also a 'programmers' network, and I don't even begin to know where that fits in. I, and I am assuming most people, will probably just post on Stack Overflow to be safe.  My question is, other than the short little description blurb of each one, is there a clear cut set of guidelines which what each network is intended for, what kinds of questions should go to each one, and is anything being done to encourage people to post in these newer, smaller (more specialized?) networks as opposed to just posting in big daddy Stack Overflow?  Now again, this is for computer science/programming/"why isn't this code doing what I want?" related questions, I am not saying that if I had a question about Linux or WordPress or something I would have the same confusion.


I want to draw a simple graphics rectangle\ circule in QGIS 2.12, just as i do it in ArcGIS:       I red       and installed the tool "Rectangles ovals digitizing in QGIS", but it works only when i edit a layer. I want graphics rectangle box and not editing a layer, just has in the Print Composer Layout

I'm pretty new in QGIS and i'm searching a drawing tool like it is possible to find in microsoft word or excel.  I search something very user friendly (for dummies!) to add circles, arrows, lines... with no need to create a new layer!!  Can you help me?


I'm a past-graduate in mathematics and familiar with the basics of ordinals and cardinals. My question is: how many infinities are there? There are obviously infinitely many, but since we already know that there are different kinds of infinity, the question remains for me: how many infinitely many? Is this a sensible question at all?

It's pretty straightforward to say that there is an infinite number of different sizes of infinity, but then I thought, "What size of infinity is that?"  My thoughts are that the number of unique cardinalities is equivalent to the number of real numbers, based on the fact that the cardinalities can always be ordered by increasing size. I don't really know how to prove this, though. It's mostly based on intuition, which isn't very reliable when talking about uncountably infinite sets.  I originally asked a somewhat related  at a different (and not math-oriented) forum, and the users there told me that it is not possible to talk about the number of cardinalities without talking about the set of all sets, which forms a paradox. If a set were to contain all of the different sizes of infinity, it would have to contain its own power set, which isn't possible.  However, I'm not completely convinced that it is not possible to talk about a set of all of the cardinalities. Sure, a cardinality represents a size of infinity, but I think that it should be possible to have a set of the cardinalities without having the set actually contain the various infinities. Would this avoid the above paradox?  So, is it possible to measure the number of different sizes of infinity, and what would that size be?


I was doing some simple harmonic motion problems and I came across this  describing the position, velocity and acceleration of a linear oscillator.   At the moment in time when v is 0 the linear oscillator should not be moving, only changing directions.  I'm having a hard time understanding why the acceleration is the greatest at that time (according to these graphs), since there is no velocity change.  Is it because acceleration is only the difference in velocity at two different points in time and not one?  How exactly does the change in direction affect acceleration?  edit: I found another  that answered my question. haha.

I'm studying for my upcoming physics course and ran across this concept - I'd love an explanation.


I have a form with some labels and two buttons, buttons are Yes and No.  For some reason I cannot get whether the user has pressed y or n keys on the form. If I use the same event for a textbox for example it works just fine.  private void Form2_KeyDown(object sender, KeyEventArgs e)         {             if (e.KeyCode == Keys.Y)             {                 btnYes.PerformClick();             }         }   Seems like that event never fires. Why is that?

I'm looking for a best way to implement common Windows keyboard shortcuts (for example Ctrl+F, Ctrl+N) in my  application in C#.  The application has a main form which hosts many child forms (one at a time). When a user hits Ctrl+F, I'd like to show a custom search form. The search form would depend on the current open child form in the application.  I was thinking of using something like this in the ChildForm_KeyDown event:     if (e.KeyCode == Keys.F && Control.ModifierKeys == Keys.Control)         // Show search form   But this doesn't work. The event doesn't even fire when you press a key. What is the solution?


Hello,  i guess it is the easiest way to show you in a picture what i want to do :-)  I want to have all my grafics with the same style: - color caption - frame grafic  So I have to change just the filename, and the captiontext.  Thanks in advance

I would like to expect the below output in my LaTeX.    The figure caption should be place in the bottom of the figure. The text should be plurred with opacity. How do achieve this?  My MWE is:  \documentclass{book} \usepackage{graphics} \usepackage{caption} \DeclareCaptionFormat{overlay}{\gdef\capoverlay{#1#2#3\par}} \DeclareCaptionStyle{overlay}{format=overlay} \begin{document}  \begin{figure*} \includegraphics{example-image-a} \caption{Many of the simple rexpressions in algebra can be thought of     interms of the areas of rectangles.} \end{figure*} \end{document}


In my program for a binary search tree, I am getting an error after adding an object to the tree in my main method. It is resulting in a Null Pointer exception from my Comparable implementation. My program places morse code characters in a binary search tree, so I am trying to compare objects lexicographically by their code values. Why isn't this working?  public class MorseCharacter implements Comparable<MorseCharacter> {  private String code; private char letter;      public int compareTo(MorseCharacter morseCharacter) {      String code1 = this.code;     String code2 = morseCharacter.getCode();      return code1.compareTo(code2); }      public int hashCode() {     int hashVal = 0;      for (int i=0; i<code.length();i++) {         hashVal = (hashVal*31 +code.charAt(i));     }      return hashVal; }  public boolean equals(Object obj) {     if (this == obj) {         return true;     }      if (obj == null) {         return false;     }      else {         return (this.hashCode() == obj.hashCode());         }     }   Here is the section in main method. I am parsing data from a file, I have checked and it reads this correctly.           try {         reader = new BufferedReader(new FileReader(file));         String line = reader.readLine();           while (line != null) {              String[] output = line.split(" ");             String letter = output[0];             MorseCharacter morseCharacter = new MorseCharacter(letter.charAt(0), output[1]);             BSTElement<String, MorseCharacter> bstElement = new BSTElement(letter, morseCharacter);             tree.add(bstElement);             line = reader.readLine();         }         reader.close();   Here is the error message:  Exception in thread "main" java.lang.NullPointerException: The object you are comparing to is null. at bridges.base.Element.compareTo(Element.java:207) at MorseCodeTree.add(MorseCodeTree.java:86) at MorseCodeTree.main(MorseCodeTree.java:220)   Changes to compareTo method (did not fix):  public int compareTo(MorseCharacter morseCharacter) {      if (this.code == null) {         return 0;      }      return this.code.compareTo(morseCharacter.getCode()); }

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


I know there are a lot of similiar questions about this topic. But nevertheless I am not able to solve my problem.  I want to reshape a dataset of this structure:  Country Variable    2001    2002    2003 A   Demand  8   46  776 A   Supply  4576    576 576 A   Storage 5   765 765 B   Demand  7543    76  58 B   Supply  58  5   65 B   Storage 864 3   537 C   Demand  6   48  65 C   Supply  75  86  458 C   Storage 587 58  5   to this structure (long format):  Country Year  Demand  Supply  Storage ...   I tried this command:  a<-reshape(test1, direction="long", varying=list(names(test1)[3:ncol(test1)]),    v.names="Value", idvar="Time", timevar="Year", times=names(test1)[3:ncol(test1)])   but it is not (exactly) working:  > edit(a)  Country Variable Year Value Time  1.X2001 A Demand X2001 8 1  2.X2001 A Supply X2001 4576 2  3.X2001 A Storage X2001 5 3  4.X2001 B Demand X2001 7543 4  5.X2001 B Supply X2001 58 5  6.X2001 B Storage X2001 864 6  7.X2001 C Demand X2001 6 7  8.X2001 C Supply X2001 75 8  9.X2001 C Storage X2001 587 9  1.X2002 A Demand X2002 46 1  2.X2002 A Supply X2002 576 2  3.X2002 A Storage X2002 765 3  4.X2002 B Demand X2002 76 4  5.X2002 B Supply X2002 5 5  6.X2002 B Storage X2002 3 6  7.X2002 C Demand X2002 48 7  8.X2002 C Supply X2002 86 8  9.X2002 C Storage X2002 58 9  1.X2003 A Demand X2003 776 1  2.X2003 A Supply X2003 576 2  3.X2003 A Storage X2003 765 3  4.X2003 B Demand X2003 58 4  5.X2003 B Supply X2003 65 5  6.X2003 B Storage X2003 537 6  7.X2003 C Demand X2003 65 7  8.X2003 C Supply X2003 458 8  9.X2003 C Storage X2003 5 9    Can you help me? Where is my mistake?

You can have data in wide format or in long format. This is quite an important thing, as the useable methods are different, depending on the format. I know you have to work with melt() and cast() from the reshape package, but there seems some things that I don't get.  Can someone give me a short overview how you do this?


Let $R$ be a ring and suppose the matrix ring $M_n(R)$ is semisimple. How does one proof that $R$ is semisimple?

I recently read the concept of semi-simplicity of a (not necessarily commutative) ring.  A ring $R$ is said to be semi-simple if $R$ as a left module over itself is a semi-simple module (This in turn means that each submodule (i.e, left ideal) of $R$ is a direct summand for $R$.)  I am grappling with the following question:     If $R$ is semi-simple, then so is the matrix ring $M_n(R)$.   It is a theorem that each left module of a semi-simple ring is a semi-simple module. Thus $M_n(R)$ is a semi-simple module of $R$. But this doesn't help me.  I need to show that each left ideal of $M_n(R)$ is a direct summand for $M_n(R)$. Is there a characterization  of the left ideals of $M_n(R)$ in terms of the left ideals of $R$?  Lastly, does the converse also hold?     If $M_n(R)$ is a semi-simple ring, then is $R$ necessarily a semi-simple ring?   Thanks.


What is the font used in Calculus on Manifolds (Spivak)? This question has already been asked, but not answered. Also, where can I get it (including summation symbols, parentheses, etc.)?

Is it possible to identify the font used in a specific document/picture?  Answers to this question should identify:   Possible methods to do this (perhaps one answer per method) and adequately describe how to use it (as opposed to merely stating it); Ways of finding the identified fonts, if possible (free or not); and Any prerequisites associated with the method used, if required (for example, "In order to use method X, your document has to be in format Y").   This question is meant as an FAQ, based on an . Its aim is to facilitate the community with the general procedures involved in font identification. Similar cases are solved on a per-usage basis on 's  tag.


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

Here at the Genealogy and Family History Stack Exchange we see many questions about relationship mapping which is also known as:   relationship calculation kinship terminology etc   If you are just trying to understand how to calculate "cousins and removes" then  provides an excellent guide.  However, if you are seeking an English term for a more complicated relationship between two members of an extended family, rather than asking a question like:          site users are encouraged to first review the answers below.    Note: This Q&A arises from  and is set to  to help make it canonical.


Prove $\lim_{a \to \infty} \frac{\sin a}{a} = 0$.  Attempt:  $|\frac{\sin a}{a} - 0| \leq |\frac{1}{a}|$ so $\frac{1}{a} < \epsilon \implies a > \frac{1}{\epsilon} $ So $\forall \epsilon > 0 \exists N=\frac{1}{\epsilon} : \forall a> N \implies |\frac{\sin a}{a} - 0| \leq |\frac{1}{a}| = \frac{1}{a} < \epsilon $ which means $\lim_{a \to \infty} \frac{\sin a}{a} = 0$  Is my proof correct?

So I got this assignment. And I was wondering how is it possible to get a limit from a constantly changing formula.  $$\lim_{x\to+\infty}\frac{\sin(x)}{x}$$ Can I only look in the domain $]0,2\pi[$?


This refers to leetcode problem:  Here is my code:  import heapq  class Solution: # def topKFrequent(self, words: List[str], k: int) -> List[str]: def topKFrequent(self, words, k):     results = []     wordTable = {}     for word in words:         if (wordTable.get(word) is None):             wordTable[word] = 1             continue         wordTable[word] = (wordTable.get(word)) + 1      heap = []     # print(wordTable)     heapSize = 0      for word in wordTable.keys():         node = [wordTable[word], word]         if(heapSize<k):             heapq.heappush(heap,node)             heapSize += 1             continue         if(heapSize>=k):             if (heap[0][0]< node[0]):                 heapq.heappushpop(heap,node)                 heapSize -= 1                 continue             if heap[0][0] == node[0] and heap[0][1]>node[1]:                 heapq.heappop(heap)                 heapq.heappush(heap,node)                 heapSize -= 1                 continue      # heap.sort(key = lambda x: x.freq, reverse=True);     print(heap)      for i in reversed(range(k)):         results.append(heap[i][1])     return results   The code works if all the words have different frequency, since it uses a min-heap. However, it doesn't work if they have the same frequency since it is going in reverse order, so the word that is alphabetically greater comes first which is not accepted (for example, if I have 4 words with same frequency and lets say they are a,b,c,d: my result will be d,c,b,a which is not acceptable) I am not sure how to account for this case and am stuck for 3 hours on this issue. Can anyone please help?

Input: A positive integer K and a big text. The text can actually be viewed as word sequence. So we don't have to worry about how to break down it into word sequence. Output: The most frequent K words in the text.  My thinking is like this.    use a Hash table to record all words' frequency while traverse the whole word sequence. In this phase, the key is "word" and the value is "word-frequency". This takes O(n) time.  sort the (word, word-frequency) pair; and the key is "word-frequency". This takes O(n*lg(n)) time with normal sorting algorithm.  After sorting, we just take the first K words. This takes O(K) time.    To summarize, the total time is O(n+nlg(n)+K)， Since K is surely smaller than N, so it is actually O(nlg(n)).  We can improve this. Actually, we just want top K words. Other words' frequency is not concern for us. So, we can use "partial Heap sorting". For step 2) and 3), we don't just do sorting. Instead, we change it to be  2') build a heap of (word, word-frequency) pair with "word-frequency" as key. It takes O(n) time to build a heap;  3') extract top K words from the heap. Each extraction is O(lg(n)). So, total time is O(k*lg(n)).  To summarize, this solution cost time O(n+k*lg(n)).  This is just my thought. I haven't find out way to improve step 1). I Hope some Information Retrieval experts can shed more light on this question.


I'm trying to find a formula for the partial sum of $n/2^n$.  I've tried this so far...  $$ S_n = \frac12 + \frac24 + \frac38 + \cdots + \frac{n}{2^n} $$  Then I tried to find a way to eliminate most of the terms by multiplying the whole sequence by $\frac{2^n}n\cdot\frac{n+1}{2^{n+1}}$ (a terms that should take each term in the sequence to the next term.)  $$ \frac{n+1}{2n} S_n =  \frac24 + \frac38 + \cdots + \frac{n+1}{2^{n+1}} $$  Then  $$ S_n- \frac{n+1}{2n} S_n = \frac12 - \frac{n+1}{2^{n+1}}$$  $$ S_n = \frac{\frac12 - \frac{n+1}{2^{n+1}}}{1-\frac{n+1}{2n}} $$  But, alas, this does not give the correct answers.  Can someone point out where I went wrong?  Thanks

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!


Prog 1:   #include<stdio.h>  int main()  {      int i=0;      while(i<=8,i++);      printf("%d",i);      return 0;   }   Prog 2:  #include<stdio.h>  int main() {   int i=0;   while(i++,i<=8);   printf("%d",i);   return 0; }   The output of Prog 1 is 1 and that of Prog 2 is 9.  Can someone explain whats going here. How the two codes are different?


Let $a$ and $b$ be positive integers. How can I easily prove that if $ab$ is a perfect square and $GCD(a,b)=1$ then $a$ and $b$ are perfect squares.   I actually managed to prove that this way:  if an integer $n$ is a perfect square, then all the powers of the prime numbers of its integer factorization are even. So if an integer is not a perfect square, then at least one the prime numbers of its integer factorization is odd.  Then, reasoning by the absurd, we suppose that $a$ and $b$ are not perfect squares and considering that their GCD is 1, no prime number of its integer factorizations is the same, so $ab$ is not a perfect square, which is absurd.  Even if this proof seems convincing, I'd like to know if it was possible to solve the problem another easier way (In exam conditions, I'd have to prove the proposition that if "if an integer $n$ is a perfect square, then all the powers of the prime numbers of its integer factorization are even" considering that it's not included in the course given by the teacher, so It would get a little tedious)

Show that if $n$, $a$, $b$, and $c$ are positive integers with $\gcd(a, b) = 1$ and $ab = c^n$, then there are positive integers $d$, and $e$ such that $a = d^n$ and $b = e^n$.   I know that (by Bezout) $\gcd\left(a,b\right) = 1$ implies $ax + by = 1$ for some integers $x$ and $y$, and also that $\gcd\left(a^n,b^n\right) = 1$, but this does not help me.


I have basically the same problem as was asked in , namely Gnome-shell leaves one monitor fixed when I switch workspaces. I would like to be able to have both monitors switch workspaces at the same time, so that I have more total screen space to work with.  Neither of the two solutions ( and ) solve the problem for me. Since both of those solutions are from 2011, 3 years ago, I wonder if something has changed, and if there is some new solution to this problem (or alternatively, has someone had those solutions work for them, which means there's something wrong with my set up).

Gnome-shell seems to like to leave one monitor as "fixed" when you switch workspaces.  Additionally, there is no preview in the Activities view of my secondary monitor.  Also, on the second monitor, where there should be either empty desktop space, or a copy of the panel, I just have a white bar.  How can I get gnome-shell to treat my secondary monitor like the primary one?


Theorem: $AB$ and $BA$ have the same eigenvalues, where $A_{n\times n}$ and  $B_{n\times n}$, and $\alpha\neq0$  Step 1: Let $v$ be an eigenvector corresponding to the eigenvalue $\alpha\neq0$ of $AB$. $ABv=\alpha v$ and by definition $v\neq0$. We are looking for a vector $w$ such that $BAw=\alpha w$ 2. If we apply $B$ to both sides of $ABv=\alpha v$, we have $BABv=B\alpha v=\alpha Bv$. Then, $BA(Bv)=\alpha (Bv)$ and $w=Bv$. If we can show that $Bv\neq0$ then $w$ is an eigenvector, $\alpha\neq0$ is an eigenvalue of $BA$, and $AB$ and $BA$ have the same eigenvalues when $\alpha\neq0$. 3. $\alpha\neq0$ and take $Bv=0$. If $Bv=0$, $ABv=0=\alpha v$. As $v\neq0$, $\alpha=0$, however this is a contradiction and therefore $Bv\neq0$ and $w$ is an eigenvector. As $w$ is an eigenvector, $\alpha\neq0$ is an eigenvalue of $BA$, and $AB$ and $BA$ have the same eigenvalues when $\alpha\neq0$. Q.E.D.

First of all, am I being crazy in thinking that if $\lambda$ is an eigenvalue of $AB$, where $A$ and $B$ are both $N \times N$ matrices (not necessarily invertible), then $\lambda$ is also an eigenvalue of $BA$?  If it's not true, then under what conditions is it true or not true?  If it is true, can anyone point me to a citation?  I couldn't find it in a quick perusal of Horn & Johnson.  I have seen a couple proofs that the characteristic polynomial of $AB$ is equal to the characteristic polynomial of $BA$, but none with any citations.  A trivial proof would be OK, but a citation is better.


I am  blender beginners, but I am experiencing this problem. I need to build a cap model. I don't know how to build a curved edge

How can I deform one edge or multiple edges of a plane or cube so they are tapered in and rounded equally?


I was using Ubuntu 14.04 LTS, and the update window appeared. I did update and then when my PC restarted I had and still have this screen.    I know if I open grub and enter recovery mode:    I could reset the root password, but when I enter recovery mode it loads all files but when it finishes, the expected screen with options doesn't appear and I get a screen like the first one.  I have more than one recovery mode, but it's always the same, I get the login screen again.  What should I do?

I am trying to boot Ubuntu on my computer.  When I boot Ubuntu, it boots to a black screen.  How can I fix this? Table of Contents:


I am in survival and I even tried creative but when I break any block (in this case a stone block with a diamond pickaxe) it just reappears. I'm using version 1.7.9 and earlier today (18th of June) I was able to most normally break blocks. I've been playing this world for a while and it still won't work.  How do I fix this?

I'm playing on a Survival world with cheats on, "easy" difficulty, and at night in-game. I didn't have a sword or anything to make a sword with, and I was starving, so I switched to Creative to give myself a stack of food and a bed to set my spawn point. When I switched back to Survival, I couldn't destroy or place blocks. I'm on single player, and my Internet is fine, and I can destroy blocks still if I switch to creative. I've tried resetting the button one, and reloading the map, and it still doesn't work. I've even tried deleting everything I gave myself in Creative. This happened before on a different world and I ended up deleting it.  This only happens on this world. How do I fix it?  If I know I'm in the correct game mode, what else can cause this?  Are there different causes in multiplayer?


What is the path of a particle if it is continuously acted upon by a force perpendicular to its velocity (given that acceleration magnitude is never equal to $v^2/r$)? Is it still a circle?

In a circular motion the acceleration is always perpendicular to the velocity. But is the converse true? If yes then is there any rigorous mathematical proof behind it? This caused a confusion when I learnt about the Lorentz Force and every source I referred quoted that 'As this force is perpendicular to the velocity, it acts a centripetal force and hence it moves in a circle' So does it always imply that an acceleration perpendicular to the velocity results in a centripetal force?


Well my question is unique. Because I want to know how can I install Ubuntu from HDD or a USB while the answer provided within the link someone said is duplicate is actually on how one can install Ubuntu from a DVD. I don't have any blank DVD to burn. So I want to install Ubuntu DIRECTLY from HDD mainly. But if it is not possible then I can install from USB too.  I am completely new in Linux world. Just want to taste Ubuntu as I listened lots of sweet words about it. However I just downloaded  ubuntu-14.04.2-desktop-i386.iso   My machine is processor Intel 2.50GH core i5, Intel main board, 2GB RAM, 500GB HDD. I am using windows 7 on C:\ drive. I want dual booting. Existing windows 7 with Ubuntu ubuntu-14.04.2. Can anyone tell me....  1- How can I install Ubuntu on Drive J:\ so that I will get dual booting.   Ubuntu with Windows 7?  2- Alternatively I can install from a USB too. Can you tell how to install from USB?

I tried to use the usb-creator.exe from Ubuntu 10.10 desktop i386 ISO image and it does create an USB stick that doesn't boot. When I try to boot from it I get:     Operating System not found.   I try to do this from Windows 7 x64. I'm not looking to create a live Ubuntu media, only an installation USB disk.  I repeated the process several times and I even tried to reformat the USB drive (FAT32), no success yet.  The USB stick is a 8GB one.


So I didn't realize my oven was broken until 10 hours after I had my pork shoulder in there. I realized it and then cooked it for 16 hours at 220F. What are the risks of eating this after 16 hours of cooking?

If I left food out of the refrigerator for some period of time, is it still safe? If I left it out too long, can I salvage it by cooking it more?


Let $A = 4444^{4444}$;  Then sum of digits of $A = B$; Then sum of digits of $B = C$; Then sum of digits of $C = D$;  Find $D$.  What should be the approach here?


I'm searching for a webshop which provides the following:   The shop offers digital goods (like mp3) User can buy a voucher / gift card @Reseller (Or there is a code provided in the CD) User can enter his code @ webshop and gets the download (unregistered) User can enter his code @ webshop and download is added to his/her library (registered)   optional: Resellers can buy codes from the Webshop  I already tried prestashop as it looks quite nice. But it needs a lot of custom programming (and has a very strange voucher-system). Customer has to add the File into the basket and add the voucher at checkout. I want to skip that ;)  Is there a Webshop (Or CMS + Plugin) which provides the things I need? (it could also be a CMS with a Storage/Folder Plugin (like joomla + K2) and a possibility to activate downloads via unique Codes.)  Any ideas are highly appreciated :)  Thanks in advance.

This is a general, community wiki  question to address  "I need a eCommerce script that does x, y, and z..." questions.  If your question was closed as a duplicate of this question and you feel that the information provided here does not provide a sufficient answer, please open a discussion on .    I have a list of features that I want for my website's eCommerce script - where can I find a script that includes all of them?


I've been asked by a colleague which one of those is correct or if they are both corrects. The "what" sentence sounds perfect and natural for me, but the "which" one does not sound right or natural... and for that reason, I just can't explain why I believe so.   If I may ask, are my assumptions right?  Thank you.

Most of the time one or the other feels better, but every so often, "which" vs. "what" trips me up.   So, what's the exact difference and when should you use one or the other?


I found this result in so many books and I tried to demonstrate it but I'm not convinced with my proof,  if A is a countable dense subset of $\mathbb{R}$ then there exists $B\subset A$  dense and countable in $\mathbb{R}$.

I am not sure if what I am looking for even makes sense (or) exists. Anyway I would be happy if someone can clear my confusion.  The set of real numbers $\mathbb{R}$ is obtained as completion of $\mathbb{Q}$. However, $\mathbb{Q}$ is not the only set which is dense in $\mathbb{R}$. $\mathbb{Q} \backslash \mathbb{Z}$ is also a dense subset of $\mathbb{R}$. I am wondering if it makes sense to talk of the "smallest" dense subset of $\mathbb{R}$. To phrase what I am looking for precisely and what I mean by smallest, I am looking for a dense set $A$ of $\mathbb{R}$ such that if $B$ is a proper subset of $A$ then $B$ is not dense in $\mathbb{R}$. I am able to "see" that the set $A$, I am looking for doesn't exist since any open interval consists of infinite rationals. But I am unable to precisely argue out to myself and convince why $A$ doesn't exist. Could some one throw more light on this?


I am searching for a query to find the details of highest paid employee in the entire organization. I am using oracle DB.  Queries which I tried are:  select * from EMP order by SAL desc FETCH FIRST 1ROW ONLY;      ERROR: SQL command not properly ended   select * from EMP order by SAL desc where rownum = 1;      ERROR: SQL command not properly ended   select * from EMP order by SAL desc LIMIT 0 , 1;      ERROR: SQL command not properly ended

Is there a way to make an Oracle query behave like it contains a MySQL limit clause? In MySQL, I can do this: select *  from sometable order by name limit 20,10  to get the 21st to the 30th rows (skip the first 20, give the next 10). The rows are selected after the order by, so it really starts on the 20th name alphabetically. In Oracle, the only thing people mention is the rownum pseudo-column, but it is evaluated before order by, which means this: select *  from sometable where rownum <= 10 order by name  will return a random set of ten rows ordered by name, which is not usually what I want. It also doesn't allow for specifying an offset.


I have a problem with chemmacros counter. When I type the reaction in different chapter, the counter of the equation doesn't restart. See the example  \documentclass[twoside]{ecsthesis}       \graphicspath{{../Figures/}}   \usepackage[sort &compress]{natbib}   \usepackage[noprefix]{nomencl} \usepackage{chemmacros} \usepackage{longtable} \usepackage{wasysym} \usepackage{hyperref} \usepackage{cleveref} \usepackage{upgreek} \usepackage{epigraph} \usepackage{tipa} \usepackage{array}  \setlength\epigraphwidth{8cm} \setlength\epigraphrule{0pt}  \begin{document} \chapter{1}  \begin{reaction} A+C=B  \end{reaction}  \chapter{2}  \begin{reaction} A+C=B  \end{reaction}   \begin{reaction}  A+C=B   \end{reaction}   \chapter{3}   \begin{reaction}  A+C=B   \end{reaction}   \begin{reaction}  A+C=B   \end{reaction}  \end{document}   I think that changing something in the .sty file could help but I do not have a clue about it.

Some document elements (e.g., figures in the book class) are numbered per chapter (figure 1.1, 1.2, 2.1, ...). How can I achieve continuous numbering (figure 1, 2, 3, ...)?  And vice versa: Some document elements (e.g., figures in the article class) are numbered continuously. How can I achieve per-section numbering?  \documentclass{book}% for "vice versa" variant, replace `book` with `article`  \begin{document}  \chapter{foo}% for "vice versa" variant, replace `\chapter` with `\section`  \begin{figure} \centering \rule{1cm}{1cm}% placeholder for graphic \caption{A figure} \end{figure}  \end{document}   Bonus question: Is it possible to adjust the numbering of the sectioning headings themselves? Can I, e.g., switch from per-chapter to continuous numbering of sections in the book class?


I am not interested in a plugin to do a fancy print, I'd just like for the content to be spread out on the page.   I have hopefully attached a page from each of the four sites I recently joined to illustrate the issue. I print because, so far, I find no bookmark capability here.  Instead I have found if I record the question number. Google will find it usually first: sustainability 4974 or for sure with: sustainability "/questions/4974"

So I have to print some Stack Overflow pages and bring them around. Just accept it.  Problem: while pages may look perfectly normal on the web, something recently broke the print layout... a huge whitespace block showed up on the right (, ). Tons of whitespace. This is on every site on the network () on a bunch of different screens ().  Futzing with DevTools, the problem seems to be :   #mainbar, .mainbar {     width: calc(100% - 300px - 24px); }   Can someone check if this is the only issue and possibly fix this?


1) You and I will play in the evening.      2) I and You will play in the evening.   I think both sentences are right, but why do we always prefer to use the first sentence?

I've been told to put "I" at the last part of the subject, as in "My sister and I walk to school." Is saying "I and my sister walk to school." wrong?


Is there any way to create something similar to an object member function on a C struct? I have been doing some work with C and I am curious about how I can create some sort of encapsulation

What are some ways to write object-oriented code in C? Especially with regard to polymorphism.    See also this Stack Overflow question .


Can we use since and for with past tense?   If we can use them, then what is difference between:         I have learnt English for 3 months   I learnt English for 3 months

When you returned, I had been at home since 10 minutes.   When you returned, I had been at home from 5 minutes.  In such sentences, is it correct to use since or from? When since is used?


so, every time I try to render my image, i just get a bunch of orange noise. i can't even see the image I'm trying to view

I am having some issues when rendering an image, my rendering screen is turning into grey even when making a full render. What am I doing wrong?


I want to be able to see all questions that I have not yet accepted as answers on all SE sites that I use (20 currently) so that I ensure I keep on top of answers. I don't believe there is any way to do this without going into each site?

I've been asking quite a few questions on several Stack Exchange sites, and I'm finding it harder and harder to keep track of them all.    Is there any way/place to see a listing of all my questions with no answer accepted on all of the Stack Exchange (2.0) sites? Or even just per site? If not, are there any plans to implement such a feature?  Although Jeff offered an answer, I don't feel it's the answer to my question; as far I'm aware there still is no way to list only my unanswered questions.


public static String[] myfunc(String s){     if (s == null) return null;     if (s == "") return new String[0];     //code..      //this code will not run if s == ""  }   I intended s == "" to cover all the empty strings. But there seems to be cases where s != "" but s.length() == 0 What is the difference between s == "" and s.length() == 0?

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?


When one looks at the sun and the moon in the sky together, why is it that the illuminated crescent of the moon does NOT "point" at the sun?  (More correctly the perpendicular bisector of the straight line joining the end points of the moon's terminator does not point at the sun. Intuitively one feels it should - as that is where the light is coming from. It is always around 20 - 30 degrees "off target".)

I live at roughly $(52.4^\circ,-2.1^\circ)$. On sunny evenings I've often looked at the Moon and the Sun and noticed that the light part of the Moon does not appear to line up with the Sun. For example, at about 17:00 GMT on 13 Mar 2011, I noticed the half Moon was facing toward a point roughly $10^\circ-20^\circ$ above where the Sun appeared to be. Why?