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Unintentional mouse movements, am I paranoid? I am having some issues trying to show multiple fields for a single label in QGIS. In QGIS2.6, attempting to display labels for a feature consisting of multiple fields results in an empty label if one of the fields is null. So for example, in the label expression dialog:  concat("Temp Site",'\n',"Notes",'\n',"Function")   will function normally unless one of the fields is null, then it results in no label being shown. Using the '||' operator instead in the expression dialog also results in the same behaviour:  "Temp Site" || '\n'  ||  "Notes" || '\n'  ||  "Function"   Is there a way to display the labels even if one of the fields is null? Black screen after installation of Ubuntu 18.04 What is the difference between image size and image quality? How to export / dump a MySql table into a text file including the field names (aka headers or column names) says:  SSH_ASKPASS    If  ssh needs a passphrase, it will read the passphrase from the    current terminal if it was run from a terminal.  If ssh does not    have  a  terminal associated with it but DISPLAY and SSH_ASKPASS    are set, it will execute the program  specified  by  SSH_ASKPASS    and open an X11 window to read the passphrase.   I'd like SSH to use an askpass program even if it was run from a terminal.  On occasion, I have to connect to servers, where there's some delay in showing a password prompt (maybe due to network issues, maybe due to attempted reverse DNS lookups, …). I get annoyed and switch to something else, and forget about the attempted connection. (Insert joke about attention span of a goldfish.) When I finally get back to it, the prompt's timed out and even a correct password would just result in a closed connection.  Keys would be one solution, but not every system I use has my usual SSH keys. However, I usually use Ubuntu systems, and Ubuntu has an SSH askpass program installed by default.  If an askpass window popped up, however, I'd be immediately aware of it. That's a good enough compromise for me, if only I can get it to work. Let $U = \{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12\}$, and $f$ be a function from $U$ into $U$.   Finally, let $F : P(U) \to P(U)$ be the function defined by  $$F(X) = \{f(x) | x \in X\}$$  For instance, if $f(x) = 13 − x$, and $X = ${1, 3, 4, 7}, then $$F(X) = \{f(1), f(3), f(4), f(7)\} = \{12, 10, 9, 6\}$$  Show that $F(A−B)$ is not necessarily a subset of $F(A)−F(B)$.    I am having trouble showing an example. Let's say:  $A = \{1,3\} , B = \{2,3\}$  $F(A) = \{f(1),f(2)\} = \{12,11\}$  $F(B) =\{f(2),f(3)\} = \{11,10\}$  Now, $F(A-B) = \{12,10\}$  $F(A)-F(B) = \{12\}$.  Hence, $\{12,10\} \nsubseteq \{12\}$ &lt;-- hmm..  By definition if $A \nsubseteq B$, there exist an $x \in A$ such that $x \notin B$. From my example, we have $x=10 \in A $ but $\notin B$. Is that sufficient?     I'm confused between the difference of $F(A-B)$ and $F(A)-F(B)$. Do you mind me / my Do the following sentences mean the same?        Do you mind if I open the window?   Do you mind me opening the window?   Do you mind my opening the window?      for me they all mean the same, bit #3 is a little less common as far as I've seen so far. Do you agree with me?  PS. I am more about the AmE register. Find all files that are NOT of a specific type/extension in folder? Linearization of PDE: $0$ is an eigenvalue since all translates of travelling waves are also travelling waves Consider the following PDE: $$ u_t=u_{xx}+f(u)-w,~~~~~w_t=\varepsilon (u-\gamma w),~~~~~~~~~(1) $$ where $f(u)=u(u-a)(1-u), 0&lt;a&lt;\frac{1}{2}, \varepsilon,\gamma &gt;0, \varepsilon\ll 1,\gamma\ll 1$.  A travelling wave for (1) is a solution that is a function of the single variable $\xi=x-ct$, i.e., $(u(\xi),w(\xi))$ satisfies $$ -cu'=u''+f(u)-w,~~~~~~-cw'=\varepsilon (u-\gamma w)~~~~~~~('=d/d\xi).~~~~~~(2) $$  If (1) is recast in a moving coordinate frame, i.e., in terms of variables $\xi=x-ct$ and $t$, it becomes $$ u_t=u_{\xi\xi}+cu_{\xi}+f(u)-w,~~~~~~w_t=cw_{\xi}+\varepsilon (u-\gamma w).~~~~~~~~(3) $$  One can see by (2), that a travelling wave is an equilibrium solution of (3). So one nearby question is to ask whether a travelling wave is stable.    For a fixed $\varepsilon$, let $U_{\varepsilon}(\xi)=(u_{\varepsilon}(\xi),w_{\varepsilon}(\xi))$ be a travelling wave for (1), i.e., an equilibrium solution for (3).          A standard technique for determining stability of $U_{\varepsilon}(\xi)$ is to linearize: If the right-hand side of (3) is linearized along $U_{\varepsilon}(\xi)$, the resulting operator is     $$ L\begin{pmatrix}p\\r\end{pmatrix}=\begin{pmatrix}p_{\xi\xi}+cp_{\xi}+f'(u_{\varepsilon})p-r\\cr_{\xi}+\varepsilon (p-\gamma r)\end{pmatrix}, $$     where $\begin{pmatrix}p\\r\end{pmatrix}(\xi)\in\text{BC}(\mathbb{R},\mathbb{R}^2):=\left\{u\colon\mathbb{R}\to\mathbb{R}^2 | u\text{ is bounded and uniformly continuous}\right\}$.      (The linearized criterion for stability of the travelling wave is that the spectrum of $L$ (except for $0$) lies in a left half-plane and $0$ is a simple eigenvalue.)  Thats the background.  Now, there is a statement that I could not understand yet.          Note, that $0$ must be in the spectrum because the translate of a travelling wave is another travelling wave.      I know that a translate of a travelling wave is again a travelling wave. But why does this imply that $0$ is in the spectrum of $L$?  Edit  After some looks at definitions, I have an idea:  Consider a solution $U(\xi,t)$ that is a translate of the travelling wave $U_{\varepsilon}(\xi)=(u_{\varepsilon}(\xi),w_{\varepsilon}(\xi))$, i.e.  $$ U(\xi,t)=U_{\varepsilon}(\xi-k)=(u_{\varepsilon}(\xi-k),w_{\varepsilon}(\xi -k)) $$ for some $k$. Then $U$ is an equilibrium solution of (3), too.  If I am not totally wrong, then we have  $$ p=u_{\varepsilon}(\xi-k)-u_{\varepsilon}(\xi),~~~~r=w_{\varepsilon}(\xi-k)-w_{\varepsilon}(\xi) $$ and  $$ p_t=0,~~~w_t=0, $$ because travelling waves are equilibria for (3) and a translate of a travelling wave is a travelling wave.  Hence $$ L\begin{pmatrix}p\\r\end{pmatrix}=\begin{pmatrix}0\\0\end{pmatrix}, $$ meaning that $$ \text{ker}(L-0\text{ id })\neq\left\{\begin{pmatrix}0\\0\end{pmatrix}\right\}, $$ because for each translate of the travelling wave, $p,r\neq 0$ and  $\begin{pmatrix}p\\r\end{pmatrix}\in\text{ker}(L-0\text{ id})$.  Hence $0$ is in the spectrum (point spectrum) of $L$.  Is this what was meant? drawing different parts of a line in different colours How to draw different parts of a line in different colours. In the following code can each part of the line be drawn in different colour      \documentclass{beamer} \beamertemplatenavigationsymbolsempty \usepackage{tikz} \usepackage{pgfplots} \begin{document} \begin{frame}[fragile,t] \frametitle{} { \begin{tikzpicture} \draw [thick, green] (2.3,1.4) +(-27:2.2cm)-- +(153:2.2cm) +(42:1.88cm) -- +(-138:1.88cm); \end{tikzpicture} } \end{frame} \end{document} How can I explain why DRM cannot work? I am looking for the shortest comprehensive way to explain to people that are trying to use DRM as a technology to prevent users from using their data in some fashion deemed undesirable, why their solution cannot work by definition.  Ideally I'd like something that:   Covers why technically it is impossible to have people access local data, but only in such-and-such a way Imparts an understanding of why this is, to avoid follow-on "But what if" rebuttals Is intuitive enough and short enough that even a politician (j/k) could grasp it   When faced with this situation I try to be clear and concise, but I usually end up failing at least on one of these points. I'd really like to have a 'stock' answer that I can use in the future. Does Windows Defender update if Windows Update is set to manual? Should I submit bank statements when applying for a UK Visa? What do they say about me? The UK Visas and Immigration Directorate publishes  that provides helpful tips that can result in successful visa applications. Section 2 of this guidance opens is entitled &quot;other documents you may want to provide&quot; (emphasis mine).  Section 2: other documents you may want to provide – all visitors This section provides guidance on the types of documents that you may want to provide to help us consider your application against the Immigration Rules. Previous travel documents/passports, which show previous travel. Financial documents showing that you have sufficient funds available.  These must clearly show that you have access to the funds, such as:  bank statements building society book proof of earnings such as a letter from employer confirming employment details (start date of employment, salary, role, company contact details) where a third party (who is either in the UK or will be legally in the UK at the time of your visit) is providing financial support to you e.g. a business, a friend or a relative, documents to show that they have sufficient resources to support you in addition to themselves and any dependant family should be provided   The first item is &quot;bank statements&quot; and this ties in with the , which says...  evidence that you can support yourself during your trip, eg bank statements or payslips from the last 6 months  (Note 'eg' is a Latin abbreviation meaning &quot;for example&quot;; this appears to be optional rather than a fixed requirement.) Question: How should someone interpret this such that the chances of success are maximized? How many statements should I submit? What are they looking for and what do my bank statements tell about me? Why does getopts only work the first time? How do I move Steam games to a new computer without re-downloading them? I have just bought a new computer and I have everything migrated over except for my Steam games.  I looked in Program Files/Steam/ and I found a folder full of the games I have downloaded, but I do not know if it is safe to just copy these folders from one computer to another (seeing as a lot of other applications will not work if you do this), or is there another recommended way?  I don't really feel like re-downloading all my games. I don't have the time nor bandwidth to download 20GB over a 1.5mbps connection.  Is it possible to contact Valve and get a disk with the games on it? How can I edit/create new launcher items in Unity by hand? Will Unity allow making custom launcher icons from .desktop files or via menu editing system? (Right now the launcher doesn't give the option to "keep in launcher" on all programs.  For some programs I use, I have to make custom launchers or .desktop files.  For instance, daily blender builds are generally just folders with an executable.  In basic Gnome or KDE, I can make a new menu entry with the menu editing system. Then, I can also add it to Docky either from the menu or by dragging a .desktop file to it. Unity launcher doesn't support drag and drop, so thats not a bug or anything, but when I open a .desktop file, it has unpredictable results. Most time it will not have "keep in launcher". Sometime it will have a pinnable item without the .desktop's icon, and if I pin the item to the launcher, it will not call upon the program again after closing it. I've also gotten it to just work with a .desktop file for celtx. Sentence vs proposition I'm reflecting upon the distinction between a sentence and a proposition in logic and philosophy. I knew that a proposition is the meaning of a declarative sentence (i.e. the abstract content of a declarative sentence, the bearer of truth-value), whereas a sentence is simply a group of words (symbols, signs) ordered according to some grammatical rule in any natural or artificial language. A sentence isn't necessarily meaningful.   According to these definitions, you could say hat a predicate like "is interesting" is a sentence. Of course a sentence like "is interesting" wouldn't express a proposition, but still, it would be a sentence. This seemed ok to me until I remembered that propositional logic is sometimes called sentential logic. But then you cannot say that "is interesting" is a sentence, because it certainly isn't a sentence in the sense of sentential logic! As a result, I'm getting confused about what a sentence is according to sentential logic.   Can someone help? Get current editor toolbar tab via Python? From what items can a wizard learn his spells? I'm now wondering after googling for a while, what are the different sources a Wizard can learn his spells from? Is it only limited to scrolls and tomes, or can a Wizard learn spells from other magic items?  The following quotes are from the PHB, page 114 Your spellbook      You might find other spells during your adventures. You could discover a spell recorded on a scroll in an evil wizard's chest, for example, or in a dusty tome in an ancient library.      Copying a Spell into the Book   When you find a wizard spell of 1st level or higher, you can add it to your spellbook if it is of a level for which you have spell slots and if you can spare the time to decipher and copy it.      For each level of the spell, the process takes 2 hours and costs 50gp. The costs represents material components you expend as you experiment with the spell to master it, as well as the fine inks you need to record it. Once you have spent this time and money, you can prepare the spell just like your other spells.   The way this is worded and considering the few examples we're given, shouldn't it be possible to learn a spell from more than just written sources?  An example would be Wand of Magic Missile: would it be possible for a Wizard to learn the spell Magic Missile by studying the spell when used by the item and write down his research and thus learning how to use the spell on his own and eventually master it?