I just noticed this (on , but seemingly applying to all Community-deleted posts):    This is awesome, and I'm concerned that it's an oversight and is meant only to be enabled for developers.  If it was an oversight... can we please keep it? Humanizing the deletion reasons would be great, but even in its current form I want it to stay.
they were question banned; it turned out it (in part) it was because of deleted questions.   was deleted by the Community user.  I'm aware it will delete old posts that have a negative score, but for a minute or two, I was really puzzled as to why it was unilaterally deleted without some notation left.  Can we have the Community user leave a notation in a post's history as to why the post was deleted?    Something like the following would suffice:     Post deleted automatically due to having negative votes and no activity for three months
Consider the function : $$f: \mathbb{R}^2 \rightarrow \mathbb{R} , (x,y) \mapsto   \begin{cases}         0 &amp; \text{for } (x,y)=(0,0) \\    \frac{x^3}{x^2+y^2}       &amp; \text{for } (x,y) \neq (0,0)   \end{cases} $$  Show that $f$ not differentiable at $(0,0)$ but all directional derivatives exist.  I don't know how to tackle this problem. Can someone give some hints or solve the problem? Thanks :) If votes works differently on meta sites how does that of accepting answers work? In the faq of meta sites you can read something like the following:     Voting here works a bit differently   from other Stack Exchange sites. On   Meta Stack Overflow, voting is used to   express agreement or disagreement, not   to point out a lack of quality or   helpfulness. Please don't be concerned   if you receive downvotes – members of   the community may simply disagree with   your bug, feature request, support   issue, or the nature of the   discussion.   My question is: If votes works differently on meta sites how does that of accepting answers work?  Take for instance a question on a meta site that is meant for the community to discuss some issue. What does it mean if the question is accepted? Accepting an answer is up to the author of the question so it cannot be a sign of what answer the community concludes from the discussion. It could mean that the discussion is over but that should be up to the community and not the author of the question. Is it so that accepting an answer for a discussion question on a meta site does not have a particular function? I am trying to run grep against a list of a few hundred files:  $ head -n 3 &lt;(cat files.txt) admin.php ajax/accept.php ajax/add_note.php   However, even though I am grepping for a string that I know is found in the files, the following does not search the files:  $ grep -i 'foo' &lt;(cat files.txt)  $ grep -i 'foo' admin.php The foo was found   I am familiar with the -f flag which will read the patterns from a file. But how to read the input files?  I had considered the horrible workaround of copying the files to a temporary directory as cp seems to support the &lt;(cat files.txt) format, and from there grepping the files. Shirley there is a better way. Proving that an integral domain has at most two elements that satisfy the equation $x^2 = 1$. Python Split String Lets Say we have Zaptoit:685158:zaptoit@hotmail.com   How do you split so it only be left 685158:zaptoit@hotmail.com After writing the FreeNAS IMG to a 16 GB USB flash drive, I can now only use 938 MB. I used the Win32 Disk Imager tool to write the IMG to the device. Then later, when I inserted the the USB drive into my Windows 7 computer it said that it had to be formatted, because it couldn't read it. I believe this is normal. So I formatted it inside Windows using the format option when prompted. So in Windows Explorer now, 938 MB is reported as capacity of this device.    Also, when i check the properties dialog box I can see the same numbers.    And when I check with diskmgmt.msc I can see there are several volumes I don't recognize and unallocated space of 12.79 GB.    Now, I have another 2 GB USB flash drive with the same problem. It too was used for FreeNAS, and it too has a reported capacity of only 938 MB. I thought it was broken there for a while, until I saw the same problem with this 16 GB model.  I tried using diskpart on the 2 GB model, and I saw that there were several partitions there (list partitions) just like on this one. So I used the clean option to try to wipe it, but that wiped off everything so it's totally useless now. I'm not sure how to rebuild it.  Is this a standard routine, like part of the whole "user experience", that whenever you make a bootable USB falsh drive with FreeNAS, it messes up your device? I am new to FreeNAS, so i wouldn't know. But it sure looks like it. Maybe it is in fact the format operation in Windows that messes things up... I don't know. It's not very nice.  How do I restore the capacity back to 16 GB-ish (14.9 GiB)? Is GNOME Terminal a type of non-login shell? Fig.1: A typical prompt, asking user for feedback/rating in iOS Background Any serious smartphone users must have seen a message similar to Fig.1 above at least once. Variations of such prompt include: &quot;Please give us 5 star ratings if you love this app!&quot;, &quot;Rate us :)&quot;, &quot;Your rating helps improve this app!&quot;, etc. Basically, Fig.1 asks user to leave a (nice) feedback/rating for the app on its AppStore(or equivalents).  The Shorter Question  When and how often should a mobile app user be asked to leave a feedback/ratings?   The Longer Question #1. Which User-statistics? What are the significant user's behavioral statistics that should be based on to generate Fig.1? For example:  Number of runs since install/reinstall of the application Time elapsed since current application run Time elapsed since first application run Time elapsed since first application install Certain events (e.g. after certain number of stages are cleared for a game app)  #2. When to Ask? If multiple user-statistics are chosen to be calculated to generate Fig.1, specifically how should the user-statistics satisfy the condition of the event? For example:  Form a unified equation (e.g. X^2+Y^2=Z^2) with all significant user-statistics partaken fairly to trigger the event. Create (multiple of) &quot;absolute&quot; event triggers (e.g. every 10th app run; elapsing 2 hours since current application run). Both of the two. Generate Fig.1 whichever comes true first. Neither of the two. &quot;There's a better way!&quot;  #3. How often? What would be the optimal min/max frequency of Fig.1 generation? By optimal, I mean users are not to be bothered too much, yet developers gain maximum output of great feedbacks from users? #4. &quot;Don't bother me again :(&quot; Should users have an option to opt-out from receiving Fig.1 at all? #5. Universal User-statistics for All Mobile Apps? Should apps under different categories be based on different user-statistics? There are significant differences in size and type of user-statistics in apps under different categories. For example, a &quot;Flashlight&quot; app is not typically run for one hour straight, while a music/movie streaming app may be run for over one hour. #6. &quot;This app does not need more feedback.&quot; Should every app of all kinds of user base ask this message? If any, should any mobile app stop generating Fig.1 when target conditions are met (e.g. downloads count, active user count, feedback count)? #7. Feedback/Rating Before Deletion Should users be asked to leave a feedback before deleting as seen in Fig.2 below? Users are more likely to leave very critical review on app deletion, but this kind of feedback will be very helpful for the developers to strengthen their app's weakness for next version release.                                                                                                 Fig.2: Asking user for rating before app deletion When to pronounce ‹s› as /z/ in the middle of words? How many injective functions $f:[1,...,m]\to{[1,...,n]}$ has no fixed point? $(m\le n)$ Number of equivalence relations on a set Resize images in PHP without using third-party libraries? Messed up my PATH environment variable and can't login to desktop To get an maven environment variable to run, I tried several options. Basically, I followed some options from , such as ~/.pam_environment, /etc/bash.bashrc and I don't really know anymore. Within them I exported sth like export PATH=/opt/apache-maven-3.6.0/bin:$PATH (I'm being so unconcrete because I cannot look it up).   Afterwards, I did run gnome-session-quit and my machine got stuck.   So after hard restart I try to login again, but I'm not able to do that: I see my username, enter the password, hit enter, screen turns black and after 2 seconds I'm back at the login screen.   So, that very strange and worrying. Next step: Login via tty (Strg + ALT + F3). Within there I can login, but can not do much. I thought about sth like . But whatever I do: The command could not be located because '\bin' is not included in the PATH environment variable. I think, altogether thats alarming and I'm getting really nervous.  Executing export PATH="/usr/bin:$PATH seems to work and echo $PATHgives an output starting with /usr/bin:/usr/bin:/usr/bin:/home/user/Documents/.../esper/examples/transaction/etc:/home/user/anaconda3/bin:/usr/lib/jvm/java-1.8.0-openjdk-amd64/bin:/opt/apache-maven-3.6.0/bin:/opt/apache-maven-3.6.0/bin:/opt/apache-maven-3.6.0/bin but does not really help.  I'm running an Ubuntu 18.04 on an Lenovo G50-70.   Can you help me accessing my desktop again and/or fixing my PATH issue? How would you evaluate $\liminf\limits_{n\to\infty} \ n \,|\mathopen{}\sin n|$ How would you evaluate the limit inferior of the sequence $n\,|\mathopen{}\sin n|$? That is, $$\liminf\limits_{n\to\infty} \ n \,|\mathopen{}\sin n|$$    Edit. Let $\mu$ be the irrationality measure of $\pi$. Since $\mu$ is not known, I will split the question:   Assuming $\mu &gt; 2$, what is $\liminf\limits_{n\to\infty} \ n\,|\mathopen{}\sin n|$? Assuming $\mu = 2$, what is $\liminf\limits_{n\to\infty} \ n\,|\mathopen{}\sin n|$?     I kind of like its graph... Oracle: function based index selective uniqueness Can you add new statements to Python's syntax? Can you add new statements (like print, raise, with) to Python's syntax?  Say, to allow..  mystatement "Something"   Or,  new_if True:     print "example"   Not so much if you should, but rather if it's possible (short of modifying the python interpreters code) Inverse of a Positive Definite Let K be nonsingular symmetric matrix, prove that if K is a positive   definite so is $K^{-1}$ .   My attempt:  I have that $K = K^T$ so $x^TKx = x^TK^Tx = (xK)^Tx = (xIK)^Tx$ and then I don't know what to do next. Random Sample vs. As Large a Sample as Possible? I'm struggling to differentiate scenarios where you would use random sampling vs. getting as large a sample as possible. For instance, one thing I am trying to test is the notion that being in a "home" arena boosts player performance.  I have collected individual football game data for every game over the past 10 years. I have over 34000 observations of players performance during this time span. Would it have been more prudent for me to take a random sample of say, 1000 players over the past 10 years?  I just don't understand why, in the above scenario, I'd take a random sample of 1000 when I can just take all of the players performances from the past 10 years. Database synchronization between dev/staging and production Converting from shapefile or raster formats to LAS?