Voting closes on March 10, Sunday! Please help select the posts to be migrated before then.

This is some kind of followup for a series of questions already in this meta site. The most relevant of them are (please note the dates, and remember some of them were posted while we were a mere beta siteling):

And today's:

After his answer on the last question, I've exchanged a few lines in chat with our new mtoad and decided to post this question.

As the matter has been discussed extensively in the links above and in some others there is no point in doing it again.

These are my conclusions, downovote if you don't agree with them, upvote if you do, run away if you can't evaluate: (for those single minded: If [!agree, downVote[], upVote[], runAway[]])

  • It isn't reasonable to bulk migrate SO Mathematica questions
  • It's highly desirable to migrate some outstanding and relevant questions. Because of the question per se, or because it received very good answer/s
  • The voting score of those jewels is not enough to judge how relevant the question is for this community nowadays
  • There are some important considerations to keep in mind while pondering if a question should be migrated:
    • Obsolescence
    • Context (older related questions/answers/comments)
    • Existing answers already covering the topic in Mathematica.SE
    • Users eventually complaining about losing rep on StackOverflow
    • Last but not least, the migrated questions will need some rework.
  • (edit by rm) Migrating old questions now is extremely difficult (disabled for posts > 60 days but occasional exceptions might be allowed — this feature has not been implemented yet), so please only consider those questions that are very very specific to Mathematica. So no general programming questions or generic questions in which Mathematica only plays a supporting role.

  • Retagging at least. Perhaps some Mma version considerations, formatting math into $\LaTeX$ (not here :S ), etc. And someone's effort (yours) needs to be available for that.

All that said, the proposal is the following: Let's make here a list of questions you consider too important to leave behind. One question per answer, and let's the community decide via (up)(down) voting if the questions should be migrated.

I propose the following simple rules, to be discussed:

  • Only one migration proposal per answer, with a link and a justification (only if needed)
  • (edit by rm) If the proposal reaches +10, the mods will go through the appropriate channels to get the question migrated.
  • If the proposal doesn't reach +10 in three months after you post it, or reaches a score of -5, it will be deleted it to avoid cluttering
  • This very question can be closed and reopened by the mods at will, depending on how the chores of migration are being handled by the community
  • 1
    "for those single minded": Are there people with multiple minds? :-) – celtschk Sep 29 '12 at 14:25
  • 5
    @celtschk We think there are, indeed – Dr. belisarius Sep 29 '12 at 15:06
  • 2
    @Mr.Wizard You closed it prematurely. I'm reopening it, with updated info. – rm -rf Oct 23 '12 at 22:58
  • It would be good to calculate a statistics of all SO questions linked from Mma.SE. It's easy to do in principle, but we can't retrieve every single question and answer from this site without special permission (my IP would be blocked) – Szabolcs Nov 26 '12 at 22:02
  • Since this will be a one time deal and as there aren't a lot of questions, then anything with a net positive number of votes should be migrated. Thoughts? – rcollyer Nov 28 '12 at 20:44

23 Answers 23


The clearest way to represent Mathematica's evaluation sequence

Both questions and accepted answer got a gazillion upvotes.

  • Excellent candidate – rm -rf Sep 30 '12 at 18:21

Performance tuning in Mathematica?

There are a few other questions on performance, but they seem to be about one particular function. This one is more general and has highly appreciated answers.


Replace inside Held expression

The Trott-Strzebonski in-place evaluation trick is described here and RuleCondition (internally used but sometimes useful symbol) is mentioned. I referred back to this more than once and I will certainly need to refer to it in the future.

This is a non-obvious but important advanced Mathematica programming technique.

  • Although we have a similar question here I vote for it because Leonid describes things as usual very detailed. – halirutan Nov 26 '12 at 22:35
  • @halirutan if you want detailed see this. Perhaps that should be recommended for migration too. – Mr.Wizard Mar 6 '13 at 16:20
  • Szabolcs, the one you linked to is already covered here (with an answer by WReach). I would suggest changing it to the very related question that Mr.W linked above. – rm -rf Mar 11 '13 at 17:41

How Plot[] works in Mathematica

Again, a very thorough answer by Alexey and this keeps getting posted as link only answers on this site... high time we brought this over here.


Strange Sin[x] graph in Mathematica

Can be merged with this question.

  • Wholeheartedly agree... we can finally put an end to and delete link-only answers that just reference this question and this one – rm -rf Sep 30 '12 at 18:23

Numbered equations/formulas

This is a popular question on SO, and might get a few additional answers here after migration.


I'd like to propose these two questions:

Data Table Manipulation in Mathematica

Data Table Manipulation in Mathematica: Step 2

where Leonid implements SQL-like 'select' and 'where' functions to handle queries on tables, a very common task.


Rolling the ball:

Version control of Mathematica notebooks

I think some users here have more to say about this topic.

  • We now have a dupe of this question. Should we merge them? – Verbeia Sep 29 '12 at 11:14
  • @Maybe just edit the question and put all further information in there is easier? Or do you think someone will add an answer on SO? – halirutan Sep 29 '12 at 13:47
  • @halirutan Who is "@Maybe"? – Dr. belisarius Sep 29 '12 at 14:06
  • it's @Verbeia ;-) – halirutan Sep 29 '12 at 14:27
  • If there's a question here, why not go ahead and answer it here? This one seems more focussed (re: workflow) – rm -rf Sep 29 '12 at 15:43
  • 2
    @belisarius - "@Maybe" should be Heisenberg, of course! – stevenvh Sep 30 '12 at 9:55
  • Simon's answer to the new question (combined with others') make it better than the original on SO and so one needn't migrate now, IMO. Thoughts? – rm -rf Sep 30 '12 at 17:24
  • Also related: stackoverflow.com/questions/8774123/… – Szabolcs Nov 26 '12 at 22:19

Best practices in error reporting (Mathematica)

I find Leonid's answer quite valuable. The answer to this question is very Mathematica-specific and doesn't apply to other languages.


How Mathematica determines that evaluation should be finished?

Interesting look at the internals of expression evaluation in general.

  • as a reference, this was the question that inspired this one, also on the list. – rcollyer Oct 1 '12 at 4:44

Making Mathematica packages

An explanation of the Mathematica package structure. Another answer that one would often want to link to, and should be maintained over time.


How does Return[] work?

Return in Mathematica is different from other languages, and has a quite complex behaviour. Questions about it will keep popping up in the future, so it is worth having and maintaining a canonical answer about it that can be linked to. The description by Leonid is rather detailed and should be included in any such canonical answers.


Symbolic derivatives are being calculated numerically

I think the answer there is a very good example on how to analyze Mma behavior


Extract information from HTML using Mathematica

This came up before on Mma.SE and will keep coming up in the future. I needed to refer back to this SO answer more than once.


Integrating notebooks to Mathematica's documentation center

This is a rather detailed tutorial on how to create documentation that integrates into the doc centre. It describes a method that doesn't require the Workbench.

It is not a great fit for StackOverflow because it's not about programming.


Why doesn't this use of Begin[] work?

An explanation of how changing the context affects parsing only. It's a trap intermediate users will run into. I have referred back to this several times, so I would like to have it here locally.


Why won't this work? Dynamic in a Select

Average question with a good answer. Already has two duplicates on mma.se (1, 2).

  • If it has duplicates here, that would be a reason not to migrate. But this is an exception because of JF's detailed answer. I was actually looking for this answer the other day (spent quite a bit of time), but I could not find it because I didn't look on SO (as usual...). So +1 because despite the duplicates this is the one to be shaped into the canonical answer. – Szabolcs Mar 6 '13 at 20:51

Creating new list with an operation applied to every element?

This may (and probably will) have been asked before on mathematica.SE, but I find it useful because it's a question every newcomer will encounter and the answers give good directions. (Maybe we can make it a canonical question?)

  • This is basically the same as the question I recently posted. The answers have a different flavor though. (My question could probably use some solutions that are more accessible to beginning users.) – Brett Champion Sep 30 '12 at 22:22

How to use FORTRAN subroutines or functions in Mathematica?

This is the kind of thing that should not be too difficult for someone who knows C and knows about calling conventions, but it's always good to have a tutorial and save some time.

This question will doubtless have duplicates here on Mathematica.SE eventually, and it is also a question that is worth maintaining and updating for new versions of Mathematica and for various FORTRAN compilers. It is better to keep this information together in one post rather than let it spread out among several posts on several sites.


Does passing a variable with a large amount of data cost a lot of memory and time in Mathematica?

We got a duplicate of this question here on M.SE just now. It would be easier and more convenient to migrate and update this one than to re-write the whole thing. Otherwise I might just end up copying and pasting the answer, with minor edits ...


What is in your Mathematica tool bag?

Since this question is currently closed on StackOverflow, I guess they wouldn't mind migrating it here. Also it's Community Wiki, so it also shouldn't affect any user's reputation, even though it is highly upvoted.

  • 1
    My personal position is "yes", but it has been discused already – Dr. belisarius Sep 29 '12 at 15:05
  • @belisarius: Ah, I wasn't aware of that discussion, thanks for the link. However, given that the question is closed over there, is there a danger for it to disappear? It would be a shame if all the good information there just disappeared (I don't know if it was already closed when it was discussed the previous time; if not, I'd say the situation has significantly changed since that discussion). – celtschk Sep 29 '12 at 15:14
  • I don't think the community should vote twice on the same thing, but yes, a closed question could be deleted – Dr. belisarius Sep 29 '12 at 15:18
  • 1
    Is it maybe an option to transform the toolbag into a blog post? This is a lot of work but it would give the hell of a post and an unbelievable resource of information. – halirutan Sep 29 '12 at 15:35
  • 1
    No, it should not be migrated. If it ever gets deleted, please let us know and we'll get it reopened by the mods. It's too mangled and inorganized to fit in here. – rm -rf Sep 29 '12 at 15:37
  • @rm-rf Ok. Please set up a trigger for me so I get alerted when someone deletes it. Thanks for your help in advance/ – Dr. belisarius Sep 29 '12 at 15:45
  • 4
    @rm-rf I personally have no strong feelings either way on this question. But just to follow your argument a little further: we aren't willing to accept the question here because it's too disorganized, but we're not going to allow the SO mods to delete it either. I'm not sure this arrangement is fair on them: it's not really our place to dictate to SO users what questions will be allowed there. Yes, we'll have to deal with it ourselves if we migrate it here, but wouldn't that be better than fobbing someone else off with it? – Oleksandr R. Sep 29 '12 at 17:28
  • @OleksandrR. That has undergone 3 closures and 2 reopens, and is a good candidate for locking, which I doubt they'll have a problem with. As for bringing it here, well, we've been incorporating elements of it in answers here, sometimes in whole. There's an entire question with 2-3 answers all by Mr.Wizard, with different variations of his dynP function, several questions on hash tables, oop-like behaviour, uses of Internal`Bag, printing definitions after stripping all internal contexts, antialiasing in 2d, 3d, Trott-Strezebonski, Villegas-Gayley, etc. (contd...) – rm -rf Sep 29 '12 at 17:46
  • So in some sense, we've transferred a lot of the information to this site and in a lot of cases, improved them. The only issue one might have is that it's not collected under a single question, but I think a lot of people are in agreement that such a behemoth post is hard to maintain. So the "keeping it alive but closed on SO" arrangement would only be till we transfer all of the content here, but there's also no need to rush to create phony questions just for the sake of it. It's better to do it organically, IMO. – rm -rf Sep 29 '12 at 17:47
  • @rm-rf I've already asked about locking it, and this was the response. – rcollyer Sep 30 '12 at 1:26
  • Also, as an added note: CW gets removed upon migration (unfortunate bug in the system...) and will have to be reapplied. But the rep gain stays – rm -rf Sep 30 '12 at 17:25
  • @rm-rf since this looks like it will be migrated, my downvote not sufficient, it looks like it should be CW and Locked once it gets over here. Of course, the rep spike won't hurt ... – rcollyer Mar 7 '13 at 16:49
  • @rcollyer No, this should not get migrated. I think that nearly all the posts there have found their way here in some form or the other and there is no need to migrate it. The overwhelming support in the meta Q referenced above is reason enough to not migrate it. – rm -rf Mar 7 '13 at 16:53
  • @rm-rf I agree it should not be migrated, except for the net upvotes. I tried to address this above, but there was no additional discussion on that point. – rcollyer Mar 7 '13 at 17:00

How would you do a PivotTable function in Mathematica?

This is a nice question with nice answer. It's a common problem that lacks from MMA built in functions.


Remove white background from an image and make it transparent

Could be merged with this question, so that we have a few additional answers.

  • This is probably better suited for Signal Processing, IMO. – rm -rf Sep 30 '12 at 18:21
  • @rm-rf Any function is a signal in some context. – Dr. belisarius Sep 30 '12 at 20:58
  • 3
    @rm-rf - Shouldn't we part with all image processing questions then? Not that I support the idea; those DSP guys may know all about algorithms but they know beans about Mathematica. They would let you write 3 pages of C++ code instead of pointing at the Mathematica ChanVeseBinarize[] function the poster asks for. After all she asks for a Mathematica solution. – stevenvh Sep 30 '12 at 23:54
  • 1
    @dreeves is a he – Dr. belisarius Oct 1 '12 at 3:00
  • @belisarius - oh, I wasn't talking about dreeves in particular, it was about all those image processing questions. I often say she for a non-specific person. :-) – stevenvh Oct 1 '12 at 7:21

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