"All Sites" has wrong information for the Japanese SO
What's with the Japanese SO's stats?
What is the best way to generate a GUID/UUID from Apex code (such as a trigger)? Preferably in the following format:     nnnnnnnn-nnnn-nnnn-nnnnnnnnnnnnnnnnn   Example:     13219ec0-3a81-44c5-a300-de14b7d0235f Are Canon EOS and Nikon DSLR lenses interchangeable? Can we use the lenses from, say a Canon EOS 550D kit (Canon EF-S 18-55mm) with a Nikon DSLR D5000 for example) ? Also, is the reverse possible ?  I'm looking at interchangeability between recent DSLR lenses only, and not with older lenses. Also, for "average" lenses, and not ultra wide/ultra zoom.  The reason for this question is that I'm trying to decide between a Nikon D5000 and a Canon EOS 500D. I like the Nikon better, but Canon is more popular here amongst people I can interchange lenses with :) Turn a string into a valid filename? I have a string that I want to use as a filename, so I want to remove all characters that wouldn't be allowed in filenames, using Python.  I'd rather be strict than otherwise, so let's say I want to retain only letters, digits, and a small set of other characters like "_-.() ". What's the most elegant solution?  The filename needs to be valid on multiple operating systems (Windows, Linux and Mac OS) - it's an MP3 file in my library with the song title as the filename, and is shared and backed up between 3 machines. Macbook Pro hard drive failing? iOS StackExchange app doesn't handle non-ASCII correctly The iOS StackExchange app doesn't handle non-ASCII characters correctly, see city name in the screenshot below. Star rating in AJAX with Ruby On Rails Consistency of an order statistic in exponential distribution I have two questions.   1) If $X_1,X_2,X_3,...,X_n$ constitute a random sample of size $n$ from an exponential distribution, show that $\bar X$ is a consistent estimator of the parameter $\lambda$.    This is my attempt: Mean of exponential distribution is $\lambda^{-1}$. Thus by central Limit theorem $E(\bar X)=\lambda^{-1}$. Using mean square consistency, if  $\lim_{n\to \infty} E[(\bar X -\lambda )^2]=0$ then $\bar X $ is consistent for $\lambda$. Since $$ E[(\bar X -\lambda )^2]= E[(\bar X)^2]+E(\lambda)^2-2\lambda E(\bar X) , $$  I get $$ \lim_{n\to \infty} E[(\bar X -\lambda )^2] =    \lim_{n\to \infty} {2 \over \lambda ^2 }+\lambda^2-2 . $$ Clearly this is not equal to $0$. How can I show this is consistent? I tried using Chebechev inequality as well. But even using that I couldn't.    2) Is $X_{(n)}$ a consistent estimator for $\lambda$? If $P[|X_{(n)}-\lambda|&lt;\epsilon]$ approaches $1$ as $n$ goes to infinity for all $\epsilon &gt; 0$ then $X_n$ is a consistent estimator for $\lambda$.    The probability density function of $X_{(n)}$ is $f_n(x) = n \lambda e^{-\lambda x}(1-e^{-\lambda x})^{n-1}$,  for $X&gt;0$.  Thus \begin{align*} P[|X_{(n)}-\lambda|&lt;\epsilon]  &amp;= P[\lambda -\epsilon&lt;X_{n}&lt;\lambda+\epsilon] \\  &amp;=P[0&lt;X_{n}&lt;\lambda+\epsilon] \\  &amp;=\int_0^{\lambda+\epsilon} n \lambda e^{-\lambda x}(1-e^{-\lambda x})^{n-1}\\  &amp;= (1-e^{- \lambda X_{(n)} }), \end{align*} where $X{(n)}$ takes values in $[0 , \lambda+ \epsilon]$.  Thus, can I say $\lim_{n\to \infty}[1-e^{-\lambda(\lambda+\epsilon)}]^n=1$? How to prove the Fibonacci sum $\sum \limits_{n=0}^{\infty}\frac{F_n}{p^n} = \frac{p}{p^2-p-1}$ How can I select first occurrence between two patterns including them. Preferably using sed or awk.  I have:  text something P1 something content1 content2 something P2 something text something P1 something content3 content4 something P2 something text   I want the first occurrence of the lines between P1 and P2 (including P1 line and P2 line):  something P1 something content1 content2 something P2 something Loop doesn't see value changed by other thread without a print statement Prove that the product of a non-zero rational and irrational number is irrational. Could you please confirm if this proof is correct?  Theorem: If $q \neq 0$ is rational and $y$ is irrational, then $qy$ is irrational.  Proof: Proof by contradiction, we assume that $qy$ is rational. Therefore $qy=\frac{a}{b}$ for integers $a$, $b \neq 0$. Since $q$ is rational, we have $\frac{x}{z}y=\frac{a}{b}$ for integers $x \neq 0$, $z \neq 0$. Therefore, $xy = a$, and $y=\frac{a}{x}$. Since both $a$ and $x$ are integers, $y$ is rational, leading to a contradiction. Clustering on the output of t-SNE I've got an application where it'd be handy to cluster a noisy dataset before looking for subgroup effects within the clusters.  I first looked at PCA, but it takes ~30 components to get to 90% of the variability, so clustering on just a couple of PC's will throw away a lot of information.    I then tried t-SNE (for the first time), which gives me an odd shape in two dimensions that is very amenable to clustering via k-means.  What's more, running a random forest on the data with the cluster assignment as the outcome shows that the clusters have a fairly sensible interpretation given the context of the problem, in terms of the variables that make up the raw data.  But if I'm going to report on these clusters, how do I describe them?  K-means clusters on principal components reveal individuals who are nearby to one another in terms of the derived variables that comprise X% of the variance in the dataset.  What equivalent statement can be made about t-SNE clusters?  Perhaps something to the effect of:     t-SNE reveals approximate contiguity in an underlying high-dimensional manifold, so clusters on the low-dimensional representation of the high-dimensional space maximize the "likelihood" that contiguous individuals will not be in the same cluster   Can anyone propose a better blurb than that? Selenium + FF : How to fix error, Unable to connect to host 127.0.0.1 on port 7055 after 45000 ms? Changing data type in ArcGIS attribute table? Exporting Data From Salesforce - REST or SOAP? Proving the total number of subsets of S is equal to $2^n$ Student here! Just reading Liebecks Introduction to pure mathematics for fun and I made an attempt at proving the total number of subsets of S is equal to $2^n$.   I realized that the total number of subsets of S is just:  $ \binom{n}{1} + \binom{n}{2} + \cdots + \binom{n}{n} + 1$  And so I put together the cool looking formula  $ \displaystyle \sum_{r=1}^n \frac{n!}{r!(n-r)!} = 2^n - 1$  But I have no clue how to approach proving this formula analytically. Any help?    So if I try a proof by induction:  $\displaystyle \sum_{r=1}^n \frac{n!}{r!(n-r)!} = 2^n - 1$  $\displaystyle \sum_{r=0}^n \frac{n!}{r!(n-r)!} = 2^n$  obviously true for $n = 1$:  $1 + \frac{1}{1!0!} = 2 = 2$  assume true for $n$, I could multiply both sides by $2$?  $\displaystyle 2\sum_{r=0}^n \frac{n!}{r!(n-r)!} = 2^{n+1}$  How could I go about proving that  $\displaystyle 2\sum_{r=0}^n \frac{n!}{r!(n-r)!}  = \sum_{r=0}^{n+1} \frac{(n+1)!}{r!((n+1) - r)!}$ Legitimate edits of less than 6 characters I recently came across an  by  which contained a link to a specification that has since been moved. When attempting to edit the link, a change which involved the subtraction of only 4 characters, I ran up against the 6 character minimum requirement.  Ordinarily this would not be an issue. A less experienced poster would likely have other things within the answer that could be changed (). In fact, this seems to be the answer on every meta post relating to this topic (, , etc...).  The problem here, since I don't have 2k reputation, is that BalusC writes excellent answers... with the reputation to back them up. I don't feel there is anything in the post (besides the link) that would benefit from me editing.  What is the standard practice here?   Flag the post and explain my situation in the notes (for someone with higher reputation)? Comment on the post and hope that a) visitors read the comments or b) the OP gets notified and updates their post? Make edits, for the sole purpose of increasing characters, providing no benefit and possibly hurting the quality of the post?   For reference, the EL Specification in the post should be changed to , if someone wants to go ahead and take care of this. asp.net mvc put controllers into a separate project How do I recover my accidentally lost Windows partitions after installing Ubuntu? I have a Toshiba satellite A-200 laptop with a Vista OS on it with 4 NTFS partitions  (C:) Vista  (D:) Entertainment  (E:) Work  (F:) Sources   and I wanted to start using Ubuntu instead. So I tried it first from the live CD and everything was OK and all the partitions were shown and working and so I decided to install Ubuntu to replace Vista on the (C:) drive. After I did that I can no longer find my folders and files on the (D:), (E:), (F:) partitions and the only file system that is shown is one 198 GB although my HDD is 320 GB.  I can't access the lost data on the remaining 120 GB which I hope is still there and not totally lost  I am now working from the live CD but I am unable to install testdisk. Can I recover the Vista partitions by the product recovery CD to get my laptop back to the factory settings? Can I recover the NTFS partitions using a recovery program for Windows or will that make the problem worse?   I need these data badly as I don't have a backup for them. Qt signaling across threads, one is GUI thread?