The other day I've learned that you cannot use "to" in the sentence "I am going (to) home". At the same time, you should use "to" with other place names. For example, I am going to work.    Could someone, please, explain the rule why we cannot use "to" with the word home? Are there any other words that we should use without "to"?
I've encountered different usages of preposition + Home and I want to learn which of them are correct.  Some examples:     Back home   Back at home   Back to home
Why should one use EM vs. say, Gradient Descent with MLE? Mathematically, it's often seen that expressions and algorithms for Expectation Maximization (EM) are often simpler for mixed models, yet it seems that almost everything (if not everything) that can be solved with EM can also be solved with MLE (by, say, the Newton-Raphson method, for expressions that are not closed).  In literature, though, it seems that many favour EM over other methods (including minimization of the LL by, say, gradient descent); is it because of its simplicity in these models? Or is it for other reasons? I've just started to play with pgfplot. I'm trying to prepare a plot like to following   \begin{figure}[h] \centering \begin{tikzpicture} \begin{axis}[minor tick num=1,  axis x line=middle, axis y line=middle, xlabel=$k$, ylabel=$\omega$, ymin=0,xmin=-2,ymax=60] \addplot[blue,domain=0:5, line width=1.5pt] {x^2+25}; \addplot[orange,domain=0:5,line width=1pt]{3*x+22.75}; \addplot[cyan,domain=0:1.5, line width=1pt,dashed]{18.166*x}; \node[coordinate,pin=right:{$v_{\phi}=\frac{\omega}{k}$}]     at (axis cs:1,17) {}; \node[coordinate,pin=right:{$v_{g}=\frac{d\omega}{dk}$}]     at (axis cs:2.5,30) {}; \node[coordinate,pin=left:{dispersion relation}]     at (axis cs:4.5,47) {}; \end{axis} \end{tikzpicture} \caption{Wave dispersion relation with phase and group velocity} \label{fig:2} \end{figure}   What I would like to do is dropping the x-y tick labels so that we just maintaing the x-y title. How can I obtain it? "Closed" form for $\sum \frac{1}{n^n}$ Earlier today, I was talking with my friend about some "cool" infinite series and the value they converge to like the Basel problem, Madhava-Leibniz formula for $\pi/4, \log 2$ and similar alternating series etc.  One series that popped into our discussion was $\sum\limits_{n=1}^{\infty} \frac{1}{n^n}$.  Proving the convergence of this series is trivial but finding the value to which converges has defied me so far. Mathematica says this series converges to $\approx 1.29129$.  I tried Googling about this series and found very little information about this series (which is actually surprising since the series looks cool enough to arise in some context).  We were joking that it should have something to do with $\pi,e,\phi,\gamma$ or at the least it must be a transcendental number :-).  My questions are:   What does this series converge to? Does this series arise in any context and are there interesting trivia to be known about this series?   I am actually slightly puzzled that I have not been able to find much about this series on the Internet. (At least my Google search did not yield any interesting results). What happened to the ia32-libs package? The ia32-libs package is no longer present in Ubuntu 12.04 repositories for a 64bit system. Are there any available replacement packages available for download? What does the tilde (~) mean at the end of a filename? What is the file with the ~ at the end of the filename for?  $ ls # aliased to add flags -rwxrwxr-x  1 durrantm  2741 May 16 09:28 strip_out_rspec_prep_cmds.sh~* drwxrwxr-x 13 durrantm  4096 May 16 14:21 ../ -rwxrwxr-x  1 durrantm  2221 May 16 14:58 strip_out_rspec_prep_cmds.sh*   This is not the same as .swp files which are there while editing.  The two files have quite a few differences and the newer file (no ~ at the end) has the most recent changes and those changes are not in the older (~) file.  Looks like I can delete it? I found several very-close-to-duplicate questions/answers. However, I want to restate some questions and discuss the answers from these questions.  Here the questions which I found:         I find it quite unfair that super simple questions and their answers upvote give the same amount of reputation points per upvote as complex questions. I think reputation points should be much closer linked to contribution. And I think that contribution in answering/asking a simple question (both in time, value and time saved to other developers) is way less than for some more complex questions.   Why doesn't Stack&nbsp;Overflow change this?  I saw several common answers:     if you change the game, then the only result is that people will game it differently.   I agree only partly with this. Sure, people will always game the system. However, any improvement can be rejected based on this argument. I believe if there is an obvious problem, it makes sense to fix it. And it looks like this question was asked number of times (meaning that it's not only me thinking that it should be changed).     Reputation is NOTHING more than an INCENTIVE to contribute.   Again. I agree only partly. Reputation doesn't have any real value (it can't be converted to anything). However, let's be honest. People are competitive and people like to have some measurement stick and most of software developers want to have a fair game. Based on this, reputation isn't NOTHING, reputation is very important tool which makes Stack&nbsp;Overflow popular. Calculating reputation one way or another way may lure or discourage people from participating.     Esoteric questions are only of interest to people working with that item.   I believe one of the biggest values of Stack&nbsp;Overflow that it contains a lot of information which is hard to find somewhere else.  So, sure, there are some rare questions which aren't valuable to the whole community. But, I would say that a question which saves 25 people a day of work (complex question) is more valuable than a question which saves a 1000 people 3 minutes of googling (simple question).  My summary:  I believe it makes sense to change a system a little bit. The simplest way would be the ability to mark a question as trivial. If some number of people marked the question as trivial (let's say 10), all upvotes for this question/answers become less valuable (for example, 1 or 2 points, instead of 5). This will close this gap. If $a_{ij}=\max(i,j)$, calculate the determinant of $A$ No space left on device -- but there is space I'm running an Ubuntu 12.04.1 server in a VMware virtualized environment that has a strange issue. Twice now, at seemingly random times, the machine has suddenly been unable to write to the root partition despite plenty of space seemingly available. I'm at a loss trying to figure out what's wrong.  "df -h" shows all mounted volumes with 40% or more free space. Both times this has happened, rebooting resolved it for a few minutes, and then it was back to saying "no space left on device." Restoring it from a snapshot seems to fix it for longer, but since this has now happened again, I'm not sure what to do with it.  If it helps, the machine is a network print server running CUPS 1.5.3 and Samba 3.6.3. Keeping chunks loaded in minecraft I have built an iron farm somewhere far away from my actual spawn chunks in my single player world. In hindsight, this was a dumb idea, but I can't exactly change it anymore. I'd like to keep the thing running all the time, so I'm looking for a way to keep the chunks loaded.  I'm running minecraft 1.12.1, is it possible at the moment? I have looked at some chunk loader mods, but chicken chunk loader hasn't been updated yet, and the others simply didn't work.  I have tried moving the spawn chunks, but that hasn't done anything either.  Edit: I have worked this out with IronAnvil, and it ended up being a render setting in optifine which didn't load them correctly somehow. It has been working fine after I reset my optifine settings to default. I'm using Xubuntu 14.04 64 bit. I know that question been asked a billion times, but all of them consist of editing following file:  /etc/polkit-1/localauthority/50-local.d/com.ubuntu.enable-hibernate.pkla   That file does not exist on my system. I tried com.xubuntu.enable-hibernate.pkla but doesn't exist either, locate command doesn't find it. One of the mysteries that my numerics class left me with are "stiff systems". Our prof didn't really manage to explain what they are. Now that the class (and the test) are over, I'm still curious.   The most concise definition about "stiff systems" I've found so far is: "There is no universally accepted definition of stiffness". So, if there is none, I don't expect one.   I'd be thankful about information on both of the following points:   From what kind of (real-world) problems do stiff systems arise? What's so "stiff" about them? What's the good thing - or the bad thing - that I'd worry about when I have to numerically solve such a real-world problem? the converse of Pythagoras Theorem Make "compact view" as a default directory view instead of "icon view" How can I make "compact view" the default for all directory views in File Manager, instead of "icon view" ? Mouse acceleration seems to be on by default, and I can't find anywhere in the launcher settings or the in game settings to turn it off.  It's very annoying as it makes it feel as if the mouse is lagging. Is there any way to turn it off? Show by induction: $(1+\frac{1}{n})^{n}<n$ Show by induction that for all natural numbers n>3  $(1+\frac{1}{n})^n&lt;n$  Let $(1+\frac{1}{n})^n&lt;n$ be true !   We show that $(1+\frac{1}{n+1})^{n+1})&lt;n+1$  $(1+\frac{1}{n})^n(1+\frac{1}{n})&lt;n(1+\frac{1}{n})$   $(1+\frac{1}{n})^{n+1}&lt;n+1$  So now we just need to show that   $(1+\frac{1}{n+1})^{n+1}&lt;(1+\frac{1}{n})^{n+1}$  So here , If I show that :   $(1+\frac{1}{n+1})&lt;(1+\frac{1}{n})$   Does that mean im done with exercise ? I'm totally new to Ubuntu/Linux, using Ubuntu Server at the moment. Just trying to  figure out something basic.   How can you tell where you are installing a program. For example I just installed Sphinx search engine by placing the tarball that I downloaded from their site to my:  /home/sphinx   directory. I created the sphinx directory to place that tarball in. Then I ran these commands:  tar xvzf sphinx-0.9.8.1.tar.gz cd sphinx-0.9.8.1/ ./configure --with-mysql-includes=/usr/include/mysql --with-mysql-libs=/usr/lib/mysql   and then these:  make sudo make install   Now I have a lot of files sitting in the directory where I ran these commands. Is this my Spynx installation or did it install somewhere else?  In windows if you run an installer (.exe file) anywhere the program will still install in your C:\Program Files directory. Does something similar apply to linux where all programs are installed in a central place, or can you install programs anywhere on the system.  Questions   I would prefer to keep all my installed programs in one place so what is the right place for this in terms of best practice. In other words what is the Linux equivalent of C:\Program Files? And how does one always install at this location, is it just a matter of placing the tarball and running the install commands from this location? What about if I use sudo apt-get to install a package. How can I point to this location to tell apt-get to always install there? What characters are valid in a Java class name? What other rules govern Java class names (for instance, Java class names cannot begin with a number)? What's the difference between a method and a function? How do I use F3 to get my coordinates when my laptop makes F3 a special key? I can't get the coordinates on my computer because it keeps changing the brightness.  I have a windows 8 Samsung, and I'm playing Minecraft version 1.6.4. C# compiler error: "cannot have instance field initializers in structs"