I have two histograms. Together they tell one story, so I want to put them in one figure. I want to stick to one column format, therefore I want them vertically. How can I do that?  I've only seen answers on how to put them next to each other horizentally.  EDIT: turns out that I can simply repeat \includegraphics twice and that's it!! Okay, so how can I put sub-label for each one? like (a) and (b) ?? so that I can talk about them in the caption?
I have 6 images, and I want to align them in this way  (a)image1 (c)image3 (e)image5  (b)image2 (d)image4 (f)image6  Any one know how to do that?  The problem for me is how to make (a), (b),..., (f) in vertical direction.
I think it's well established that for the basic premise in the Back to the Future Trilogy to work, we have a system of alternate timelines.  If this is the case though, then why would Marty in Back to the Future (the original) begin to fade?  Logically, there would simply be no Marty in the alternate timeline created when Marty travels back to 1955 for the first time; why should this affect the original Marty from the original timeline? It happens sometimes to receive or see a very good answer that arrives very late and that would deserve more upvotes. What can be done to give a boost to them? I would happily spend some of my reputation points to be able to give them such boost. This is not merely a question of reputation, but the idea is to let the answer &quot;bubble up&quot; faster so that it can be seen easily by other people to look into question. I hope I explained my question so that is understandable. Most of you got the point and there are some interesting proposals like the one that proposes to put randomly an answer at top. But I do have not enough experience to say if there is one that could solve the issue or not. I would be curious to know what Jeff thinks about it, if it feels there is something that can be improved or not. Some time ago, we announced that . This has gone well and we're extremely thankful to everyone for their support and feedback. Because it has been successful so far, we're going to be extending the program to the majority of our graduated sites. Well, we've pretty much already done that, but there are quite a few sites that have ads enabled, yet still display nothing. The thing is, we don't really have an abundance of clients offering products that a  would find relevant, but Amazon has stand mixers, a selection of super fine chinois, deliciously sharp cutlery and enough cast iron to fill the Gulf Of Mexico with . Beginning as early as this week (week of 5 February 2018), our ad team is going to be hand selecting affiliate ads to be displayed on select sites. The use of inventory will of course depend on the availability of relevant ads to display which means:  Some sites might see very few, if any ads. Some topics simply don't come remotely close to orbiting anything worth advertising. Furthermore, while graduated, some sites simply don't have enough activity for ads to make sense.  Since these are hand-selected, it could take a while for ads to appear initially.  These would of course yield to inventory from clients if clients had products that were relevant to any given topic.   Nothing changes when it comes to the . If you're used to occasionally seeing a community promotion ad, you'll just notice that you'll also occasionally see an ad for something that is likely to be of interest to someone interested in the topic that your site covers. In fact, to be clear, this is simply a continuation of the announcement we made in November of 2016. We just wanted folks to know that we're going to be continuing the program where there's good potential to show relevant advertisements, even if we don't have clients lined up with a demand for it. Where can I give feedback about a certain ad on [site]? Open a meta post on your per-site meta and let us know. Please remember, the bulk of advertisements are an effort to get something small back from folks that hit the sites through search engines and are extremely unlikely to ever become contributors. Their soufflé stopped falling, and we'll probably never see them again. Maybe we can get a few bucks once they realized that copper ions help egg whites stiffen properly and buy a bowl or a proper bloom whisk. However, you're the experts on these topics and we're very likely going to listen to you. What sites, specifically? Are any sites exempt? If you're a former Stack Exchange 1.0 site and / or subsequently joined the network under a special charter, nothing changes - don't panic :) For the rest, we're just extending what we're currently doing with ads on graduated sites to also include those where there's an opportunity to make sensible use of affiliate ads. If a site has less than 15k (average) daily visits, or fewer than roughly 50k combined total posts - it might not yet be time to invest in selecting ads to be shown there. But, part of this exercise is also seeing what works best. I don't really have feedback, just some suggestions Ads aren't just an opportunity to sell stuff, they're an opportunity to really show people that we understand a given topic. That, of course, makes suggestions from people that do that stuff every day quite valuable. Post on your per-site meta and our community / ad critters will take a look. Questions? Comments? Kvetches? Let us know in an answer or comment below. If anything about the plan changes, we'll update this post to let folks know. How to say that you have plans to go to the movies tonight (but you are not sure yet, maybe you will have a pizza)? I mean there are options:     I am going to the cinema tonight.   Way too much certainty in this. For me it means that you have already bought tickets, the least.     I am going to go to the cinema tonight.   Sounds a bit awkward.     I will go to the cinema tonight.   Sounds too formal to me. How to avoid getting shocked by static electricity? sometimes I get "charged" and the next thing I touch something that conducts electricity such as a person, a car, a motal door, etc I get shocked by .  I'm trying to avoid this so if I suspect being "charged" I try to touch something that does not conduct electricity (such as a wooden table) as soon as possible, in the belief that this will "uncharge me".   Is it true that touching wood will uncharge you? How and when do I get charged? I noticed that it happens only in parts of the years, and after I get out of the car... This is inspired by some discussions in .  In the Harry Potter universe, how are Dementors born?  Or are they artificially created by some magical means? Properly discontinuous action: equivalent definitions Let us define a properly discontinuous action of a group $G$ on a topological space $X$ as an action such that every $x \in X$ has a neighborhood $U$ such that $gU \cap U \neq \emptyset$ implies $g = e$. I would like to prove that this property is equivalent to, having given $G$ the discrete topology and in the $X$ locally compact Hausdorff case, the map $G \times X \rightarrow X \times X$ given by $(g, x) \mapsto (x, gx)$ being proper (i.e. closed and preimage of compact sets is compact) plus the action being free.  I have managed to prove one direction, that is, if the action is proper and free with $G$ having the discrete topology then it is properly discontinuous. I'm having trouble though with the other direction. Here is an attempt: let's denote by $\rho : G \times X \rightarrow X \times X$ the map $\rho(g, x) = (x, gx)$. Suppose $K \subset X \times X$ is compact. We wish to show $\rho^{-1}(K)$ is compact. Let $(g_i, x_i)$ be a net in $\rho^{-1}(K)$. Then $\rho(g_i, x_i) = (x_i, g_i x_i)$ admits a convergent subnet, so passing to it we may assume $x_i \rightarrow x$ and $g_i x_i \rightarrow y$. Essentially we must now find a way to prove $g_i$ converges, but I can't seem to do this. Any hints? Every season near the trade deadline, we see teams that are out of it trading expensive players and/or free agents-to-be, typically for younger players or prospects.  For example, Matt Garza, set to become a free agent after the season, was traded to the Rangers for a few prospects.  It made sense for the Cubs to trade Garza, because he wasn't under contract any further than this season, and thus doesn't have much value to them.  Compare Garza to someone like Mike Trout, who is likely the most valuable property in baseball, given his skill and inexpensive cost over the next several years.  There's no way the Angels would trade him, because he'll be the cost-controlled centerpiece of the team for years to come.  However, with the Angels out of it this year, what if they wanted to trade Trout to a contender (say the Pirates), but only for the remainder of this season?  That is, they'd get several top prospects now, and would have an agreement with the Pirates that they'd trade him back in the offseason (for something pretty worthless, say for a journeyman minor leaguer).  The Pirates get Trout for the stretch run and are happy to give up a few prospects.  Trout doesn't have much value to the Angels this year, but he has a ton of value for next year.  So they get a few prospects for him, in exchange for the part of his career which has very little value to them.  So in effect, the Pirates are renting or borrowing him for the remainder of 2013.  Why don't trades like this happen?  Are there any rules prohibiting trades like this? How do you express that your understanding of something is completely changed? When something blows your mind and changes your understanding of something that you've believed in for years, how do you express it (formally or informally)? Calling C/C++ from Python? What would be the quickest way to construct a Python binding to a C or C++ library?  (I am using Windows if this matters.) Stack Overflow as a reference in a professional paper/presentation Suppose I'm doing an academic paper, journal article, or other professional presentation.  Would you say that it would be possible to use Stack Overflow as a reference?    Of course I'm pretty sure that the answer here would be "yes."   So here's the follow up: When, if ever, would it be a good idea to cite a Stack Overflow question as a reference in an professional paper/presentation of some kind? Cause of Alpha or Black Artefacts in Render Evolution threads extra lines before signature Suppose a package provides whatever.service file so certain events (including whatever.socket) cause a daemon to start with a certain configuration.  I want to disable this completely. In particular, I want the old socket and any other unit files that might refer to this service by name to be unable to start the daemon.  Instead, I want to create my own unit files for this daemon with a different .socket unit and different environment variables. I also want my override to automatically take account of possible upstream updates to the original unit file (which my current solution of copying whatever.service as whatever-modified.service and editing it unfortunately does not provide).  If I create the following symlinks and files: /etc/systemd/system/whatever.service → /dev/null /etc/systemd/system/whatever-modified.service → /usr/lib/systemd/system/whatever.service /etc/systemd/system/whatever-modified.service.d/fix.conf  systemd considers the new service to be masked as well and refuses to start it. How to avoid this? How can I get this symbol without using bbold? How will the super massive black hole affect our galaxy? Three linked question on non-negative definite matrices. 1.a symmetric matrix in $\mathbb{M}_n(\mathbb{R})$ is said to be non-negative definite if $x^Tax≥0$ for all (column) vectors $x\in \mathbb{R}^n$. Which of the following statements are true? (a) If a real symmetric $n\times n$ matrix is non-negative definite, then all of its eigenvalues are non-negative. (b) If a real symmetric $n\times n$ matrix has  all of its eigenvalues are non-negative , then it is non-negative definite. (c) If $ A\in \mathbb{M}_n(\mathbb{R})$, then $AA^T$ is non-negetive definite. 2. only one of the following matrices is non-negetive definite. Find it. (a) $\begin{pmatrix} 5 &amp; -3 \\ -3 &amp; 5 \end{pmatrix}$. (b) $\begin{pmatrix} 1 &amp; -3 \\ -3 &amp; 5 \end{pmatrix}$. (c) $\begin{pmatrix} 1 &amp; 3 \\ 3 &amp; 5 \end{pmatrix}$.      3.let $B$ be the real symmetric non-negative definite $2×2$ matrix such that $B^2=A$ where $A$ where is the non-negetive definite matrix in question $2$.write down the characteristic polynomial of $B$.      My thoughts..  For1.  (a) &amp; (b) are true but not sure about (c). For 2. (a) is the correct option since it has all positive eigen values.they are $2,8$. For 3. Eigen values of $B$ will be $\sqrt{2}$ and $\sqrt{8}$. So the answer is $x^2-3√2x+4=0$.      Can anybody help me to verify the solutions of the above problems. I'm consistently receiving significant delays on Stack Overflow when opening the flag dialog on questions. Delays do not occur on any other StackExchange site I have checked. This started a couple days ago (as far as I can tell).  Delays occur not only when loading the initial screen, but also when loading the submenus. This is slightly confusing for a couple seconds (until you're used to it) since it appears as if the flag dialog has simply vanished.   What's going on here? I demand to know, otherwise somebody will be very upset.  Not me. I'm not going to get that upset over something like this.  But someone will.    Specs (though I know of several others who have this issue):  Windows 7 64-bit Chrome Version 30.0.1599.69m     Ping: 31ms Download: 6.88mbps   Upload: 1.07mbps How can I swap or replace multiple strings in code at the same time? How do I edit an invalid sudoers file? It throws the below error and it's not allowing me to edit again to fix it.  Here is what happens:  $ sudo visudo &gt;&gt;&gt; /etc/sudoers: syntax error near line 28 &lt;&lt;&lt; sudo: parse error in /etc/sudoers near line 28 sudo: no valid sudoers sources found, quitting