How Could Stack Overflow Support "What's the Best X" Questions? I've noticed that "What's the best..." questions are both popular and against the rules on Stack Exchange sites.  I've also noticed that getting the pulse of the brilliant tech community that uses these sites is extremely valuable. If I want to find a good blog platform, JavaScript MVC framework, or shared text editor, the SO users typically know the newest, technically soundest, most popular and functional ones.  Is there room on Stack Overflow to enable this kind of subjective question? Maybe it could be a new Stack Exchange site, like "bestInClass.stackexchange.com" or different category of question, meant to be opinion based.  I see one similar question, but I'm open to any implementation of the "Best In Class" pattern. Maybe if you ask that category of question the reputation is calculated differently, or in a separate container. Maybe SO rep counts towards some weight on your opinion of what is the best in class.  I think there's a solvable and lucrative problem here:   You have a user base with valuable knowledge (What's the best XYZ?) They are willing to share that knowledge It doesn't fit within the SO model   If #3 could be solved, "What's the Best X" could be a great addition.  Similar:
Give each site a parallel site for polling, recommendations and subjective-ish stuff Stuff like polls, recommendations based on subjective constraints, puzzles, webcomics etc. do not belong on the serious main SE sites, where professionals should be considered at work and having just a few spare minutes ("code's compiling") to answer questions, so they should not be distracted by such things. However, I'd also like to have a home for these things still using the SE engine. For the reason I mentioned before, this needs to be a separate place though. Let's call it four.[sitename-here].com.
relation between $R^2$ of simple regression and multiple regression A very basic question concerning the $R^2$ of OLS regressions   run OLS regression y ~ x1, we have an $R^2$, say 0.3 run OLS regression y ~ x2, we have another $R^2$, say 0.4 now we run a regression y ~ x1 + x2, what value can this regression's R squared be?   I think it's clear the $R^2$ for the multiple regression should be no less than 0.4, but is it possible for it to be more than 0.7? I have a VF page built on Lightning Design system (LDS) framework. When I add the renderAs="PDF" attribute, pdf does not show the content with LDS CSS/Style.  Reference Link:   Note1: apex:page tag has all the usual attributes which is required for pdf *     (showHeader="false" sidebar="false" standardStylesheets="false"   docType="html-5.0" applyHtmlTag="false" applyBodyTag="false")   Note2: Salesforce supports external stylesheet. That is, CSS file stored in Static resource. Link of example:   I also copied the whole css content from the LDS CSS file (Path: 'assets/styles/salesforce-lightning-design-system-vf.min.css') and applied as inline CSS in VF page. But still, there is no luck.  My styleSheet is referred in VF page as below  apex:stylesheet value="{!URLFOR($Resource.SLDS221,      'assets/styles/salesforce-lightning-design-system-vf.min.css')}"   Page works absolutely fine if it is not rendered as PDF.  Any suggestions? Database design for products with bundles of products I am building a database system for my retail business. I have set some tables which are:   Product Purchase Sales Balance   All are connected one another and are able to show my inventory level.  The problem I am having is I also sell bundles of products - that have different prices than their individual prices. Example: I sell an orange for $1, an apple for $1.2; I sell fruit package 1 (2 oranges and 2 apples) for $3.8, package 2 (4 oranges and 4 apples) for $7.  Is there a right way how to create relationship for these product bundles?  PS: I am using FileMaker Pro creating this. Login as other user setting for other profile except System Adminsitrator If a user is setup as System Administrator profile, the user can login as other user. However, is there any option that I can enable this function for other profile except System Administrator because I don't want to give them other System Administrator permission access?  In the past as I remember in summer 12, there's an option called "managing user permission" which allow me to disable or enable the profile to login as other user. But I don't see this anymore. This is Exercise 3.1.A. in      Suppose that $\pi: X\rightarrow Y$ is a continuous map of differentiable manifolds. Show that $\pi$ is differentiable if differentialble functions pull back to differentiable functions, i.e., if pullback by $\pi$ gives mpa $\mathcal{O}_Y\rightarrow \pi_*\mathcal{O}_X$.   Let $f: V\subseteq Y\rightarrow \mathbb{R}$ be a differentiable function on an open subset of $Y$. Let $(U,\phi)$ be a chart of $X$, $(V,\psi)$ be a chart of $Y$. Then $f\circ\pi(\phi^{-1})$ is differentiable and $f\circ\psi^{-1}$ is differentiable. We need to show that $\psi\circ\pi\circ\phi^{-1}$ is differentiable. I don't know how to prove this.   Can we say that since $(U,\psi\circ\pi)$ constructs a chart of $X$, by the compatibility, $\psi\circ\pi\circ\phi^{-1}$ is differentiable? This seems true but this does not use the fact that $f$ is differentiable.  Sorry I have no background of Differentiable Manifolds. Any help would be appreciated.  I also saw this post: , but I don't understand how $\gamma$ is smooth in the answer. $\gamma=\beta\circ\rho$, where $\rho$ is defined to be smooth, but $\beta$ is not. Is it possible to search for down voted questions? I want to search for new downvoted questions to improve or flag them.   I tried in the searchbar: votes:-1 is:question   but votes:XX only works with positive numbers. I can't query for downvoted questions. Is there a work-around to this? If there's not, should this feature be added? Why can a function modify some arguments as perceived by the caller, but not others? I'm trying to understand Python's approach to variable scope. In this example, why is f() able to alter the value of x, as perceived within main(), but not the value of n?  def f(n, x):     n = 2     x.append(4)     print('In f():', n, x)  def main():     n = 1     x = [0,1,2,3]     print('Before:', n, x)     f(n, x)     print('After: ', n, x)  main()   Output:  Before: 1 [0, 1, 2, 3] In f(): 2 [0, 1, 2, 3, 4] After:  1 [0, 1, 2, 3, 4] Variance of the future value of a cash flow I want to compute the variance of $FV =A\sum_{k=1}^n(1+r)^k=:g(r)$, assuming interest rate $r\sim\mathrm{N}(\mu,\sigma^2)$ and constant equal payments $A$. As discussed in the comments, the Delta Method gives an approximation $\mathrm{Var}[FV]≈\sigma^2\times(g′(\mu))^2$. Is there a way to get an exact answer? Is there an easy way to remove overlapping faces? In the example remove doubles doesn't work  You might be able to do the following: A to select all faces. X &gt; Only Faces. F to create faces, but after deleting the faces I'm left with something like this.  If I press A to select all and then press F to create faces then there are still overlapping. Blend file This is problem 6.2 from the 3rd edition of Principles of Mathematical Analysis.      Problem 6.2: Suppose $f\geq 0$, f is continuous on $[a, b]$, and $\int_a^b f(x) \, dx = 0$. Prove that $f(x)=0$ for all $x \in [a, b]$.   I'm looking for a critique of my proof. It's a pretty easy problem, but I am always wary of making too bold of assumptions, especially on these low level/fundamental proofs. I'll be using Rudin's notation and refer to theorems from the text (If I should include the text of each theorem, feel free to leave a comment... I'm lazy but could probably use the TeX practice :p)  Proof: Assume, for contradiction, that $f&gt;0$. Then, for any partition $P$ we have the Lower Riemann Sum: $L(P, f)=\sum_{i=1}^n m_i \, \Delta x_i$. At least one $\Delta x_i$ must be positive, since $a &lt; b$, and each $m_i$ must be positive since we have $f&gt;0$ by assumption, so certainly $\sup f &gt; 0$. That means $L(P, f)&gt;0$. Thus, we have: $$0 = 0(b-a) &lt; L(P,f)\leq \sup L(P, f) = \inf U(P,f) =L$$ where the last string of equalities holds because our function is continuous on a compact interval, so is integrable by theorems 6.8 and 6.6. So our integral has value $L&gt;0$. This is in contradiction to our given assumption that $\int_a^b f(x) \, dx = 0$, so we must have that $f=0$ on $[a, b]$. $\Box$  So, I am wondering if my proof is correct (and is presented well). Also if someone could enlighten me as to what Rudin means when he say "Compare this with exercise 1," I'd be appreciative. Is it a hint or is there something else he expects you to notice? there are a lot of things I could compare :)...  Exercise 6.1: Suppose $\alpha$ increases on $[a, b]$, $a \leq x_0 \leq b$, $\alpha$ is continuous at $x_0$, $f(x_0)=1$, and $f(x)=0$ if $x\neq x_0$. Prove that $f$ is Riemann-Stieltjes Integrable and that $\int f \, d\alpha = 0$ Further anonymize deleted accounts by changing the username in close/delete notices When an account is deleted, the username in the user's posts and comments is changed to a generic user&lt;userID&gt;. But the username stays the same on close and delete notifications on posts the user had voted to close / delete1. I think it shouldn't, especially for users who used their real name as their username, if they chose to distance themselves from the site and remove their accounts, it makes sense that they wouldn't really want their name plastered on close and delete notifications.   A perhaps easy way to avoid the actual username remaining visible would be to change it to the generic user&lt;userID&gt; (or anything generic enough, like "anonymous") prior to deletion, and wait a bit for the generic username to propagate all over the site. If I'm not horribly misreading , this was part of the process in the old days.   This could be automated or added as a suggestion to the .  Glaring example can be seen , where the deleted user also posted a comment where their name is properly anonymized:        1 I've seen it on close notifications and self deleted answers. I'm not sure it happens on deleted questions, or deleted answers that aren't self deletions, and I don't have a way to verify it - other than stumbling on them accidentally There does not exist any integer $m$ such that $3n^2+3n+7=m^3$ I have this really hard problem that I am working on and I just don't seem to get it. The question is: let $n$ be a positive integer; prove that there does not exist any integer $m$ such that $3n^2+3n+7=m^3$.  Please explain in detail otherwise I might not understand. I am also open for any methods that might help. Thank you. Please help. If $(X_n)$ is i.i.d. and $ \frac1n\sum\limits_{k=1}^{n} {X_k}\to Y$ almost surely then $X_1$ is integrable (converse of SLLN) Let $(\Omega,\mathcal F,P)$ be a finite measure space.  Let $X_n:\Omega \rightarrow \mathbb R$ be a sequence of iid r.v's  I need to prove that if:  $ n^{-1}\sum _{k=1}^{n} {X_k} $ converges almost surely to $Y$ then all $X_k$ have expectation.  If I understand correctly then $X_k$ has expectations means $X_k$ is in $\mathcal L^1(\Omega)$.  And I know that on finite measure space Converging in expectations is converging in $\mathcal L^1(\Omega)$ and it's stronger than almost sure convergence.  And I know that from linearity of expectation even if one of the sequence is not in $\mathcal L^1(\Omega)$ then $Y$ is not in $\mathcal L^1(\Omega)$.  How do I continue? Disclaimer: I'm pretty novice at sysadmin stuff.  I'm trying to set up port forwarding in an AWS EC2 instance, this has to be done in the command-line because I don't want to go in and edit anything, it has to be automatic (it's part of a build process).   sudo echo "net.ipv4.ip_forward = 1" &gt;&gt; /etc/sysctl.conf      Permission denied   The weird thing is I've been (successfully) using sudo for pretty much every command that required su privileges. If I do sudo su before the command (trying it out by hand in an ssh session), then it works.  Reasons behind this? Possible solutions that don't involve sudo su or manual edits? I have a LAMP server with following configuration.  CPU : Intel(R) Xeon(R) CPU   RAM : 32 GB  HDD : 80 GB  Running on virtual environment.  All the things in the server are running smoothly. But I have noticed that the RAM usage is the server is increasing each day without any reason.   This is the current memory usage on my server.  # free -g              total       used       free     shared    buffers     cached Mem:            31         13         17          0          0         10 -/+ buffers/cache:          1         29 Swap:            2          0          2   And you can see the last 8 weeks memory usage below.   And i have executed the following command to find how much memory each process is consuming.  # ps -eo size,pid,user,command --sort -size | awk '{ hr=$1/1024 ; printf("%13.2f Mb ",hr) } { for ( x=4 ; x&lt;=NF ; x++ ) { printf("%s ",$x) } print "" }'          0.00 Mb COMMAND        2253.62 Mb /usr/libexec/mysqld --basedir=/usr --datadir=/var/lib/mysql --user=mysql --pid-file=/var/run/mysqld/mysqld.pid --skip-external-locking --socket=/var/lib/mysql/mysql.sock        1171.66 Mb java -jar /etc/vmagent/bin/VMAgent.jar         138.27 Mb /sbin/audispd         127.75 Mb /usr/sbin/named -u named -c /etc/named.conf -u named -t /var/named/run-root          74.29 Mb auditd          73.03 Mb automount          43.14 Mb /usr/bin/spamd --username=popuser --daemonize --nouser-config --helper-home-dir=/var/qmail --max-children 5 --create-prefs --virtual-config-dir=/var/qmail/mailnames/%d/%l/.spamassassin --pidfile=/var/run/spamd/spamd_full.pid --socketpath=/tmp/spamd_full.sock          43.14 Mb spamd child          43.14 Mb spamd child          37.13 Mb /usr/sbin/httpd          37.02 Mb /usr/sbin/httpd          36.52 Mb /usr/sbin/httpd          36.46 Mb /usr/sbin/httpd          36.23 Mb /usr/sbin/httpd ................   For troubleshooting , i have restarted the MySQL and APACHE servers. But the result was same. Restarting the entire server will fix the issue, but i want to know what is the real issue.  Let me know if you have any idea about this issue.  Thanks,  Arun S If $x,y$ are positive reals such that $x+y = 2$ show that $x^3y^3(x^3+y^3) \leq 2$.   I thought about working backwards on this one. We can try to prove that $x^3y^3(x^3+y^3) \leq 2$ is true by first realizing that $x^3+y^3 = (x+y)(x^2-xy+y^2)$ and substituting in for $x+y = 2$. We then get $x^3y^3(x^2-xy+y^2) \leq 1$. How do I prove this is true? Is it possible to disable X at boot time? I'm setting up a server so it would be nice if it wouldn't load the graphical interface every time I boot. Dual boot UEFI Windows 7 and Ubuntu 12.04 (both 64 bits). W7 entry doesn't appear in GRUB How to evaluate $ \lim_{(x,y)\to(0,0)}\frac{y^2\sin^2x}{x^4+y^4} $ Should I add a 'Home' Button to the navigation? I know that it is common behavior to have the logo of a web page be a link to the home page, but should I also have a 'home' link in the navigation bar for it as well?