Wolfram Mathematica

12:03 AM

@R.M I liked your latest answer. A good application for the Internal`Bag, that's for sure. (I would have used Do rather than For, but still...)

R.M

@OleksandrR. Oh, well :) Didn't think it would make a difference in compiled code though... does it?

Oleksandr R.

@R.M No, I don't think so (or not significantly, anyway). I just think Do is clearer.

I dare say, for someone used to C, For is perfectly good. Personally, though, I would only use it in cases requiring an unusual iteration scheme.

R.M

12:19 AM

@RolfMertig One of the main reasons I dislike ListConvolve for such signal processing applications is that you need to be explicit with all options to get the actual convolution process correctly. So an example with padded fft that demonstrates the convolution theorem would be:

ListConvolve[a, b, {1, -1}, 0] ==
 With[{len = Length@a + Length@b - 1},
  InverseFourier[
   Fourier[a ~PadRight~ len, FourierParameters -> {1, -1}] Fourier[
     b ~PadRight~ len, FourierParameters -> {1, -1}],
   FourierParameters -> {1, -1}] ]

which gives True

J. M.

1:38 AM

@SjoerdC.deVries Well, you know the rules, right? ;) C'mon...

@F'x Not really. 1. Hobbes would never actually eat Calvin. 2. Even if he did, Calvin will easily block Hobbes's alimentary canal.

R.M

@J.M. The fixed point of all games...

J. M.

@R.M Precisely. That's why it's so much fun, just like Mornington Crescent...

Hey, since you're here: I saw this answer of yours only now. About Goertzel's algorithm... have you seen this?

R.M

1:53 AM

@J.M. I'm aware of Goertzel's algorithm, but haven't seen that reference in particular... alas, I haven't yet done any of what I wrote in my to-do list in that answer :D

J. M.

Just something I want to note. :) Goertzel can behave badly sometimes, and it's not the first thing people look at when their results look wonky... so for safety, use Reinsch's version.

R.M

Thanks for that :) I wasn't aware of it (I've never actually used Goertzel in practice; only looked at it briefly for academic purposes)

J. M.

2:28 AM

FWIW: I'm not anti-For[]; I'm just anti-ugly...

R.M

ok, ok! :P

J. M.

If For[] turns out to be the tidiest way to do the job, then hell, go ahead! ;)

R.M

In this case, it probably wouldn't have mattered anyway, but there might be cases where For might be "cleaner"

J. M.

@R.M I wasn't teasing you. ;) I saw the parts above where there was railing against For[].

@R.M Precisely; "use the proper tool for the job". I wouldn't use Do[] if the increments are not varying linearly, for instance...

(On the other hand, I'm not entirely immune to writing clunky code; I use While[True, (* stuff *) If[test, Break[]]] to fake an until loop whenever I need one...)

R.M

Well, I almost never use for in MATLAB either these days (in cases where it cannot be vectorized), instead resorting to more "functional" ways of doing the same

Oleksandr R.

2:38 AM

@J.M. :-O

J. M.

@OleksandrR. Hey, I recall needing an until at least twice... ;)

Oleksandr R.

@J.M. one can always use While[stuff; !test]--While doesn't actually have to have a body.

J. M.

@OleksandrR. Huh, so it does! Now I know... thanks! :)

Oleksandr R.

:)

R.M

Pfft... what a bunch of sissies! A real man uses Label and Goto to implement an until loop...

Module[{},
 Label[until];
 If[..., ..., Goto[quit]];
 Goto[until];
 Label[quit];
]

Oleksandr R.

2:43 AM

Well, that is certainly what the compiler will emit...

J. M.

Usually the decision to include label/goto in a language is defensible, but I can't see how I'd defend its presence in Mathematica...

There's a use for that pair, I'm sure; I'm just not seeing it...

R.M

Probably all the functionality that allows you to avoid Label and Goto needed the use of these two

Oleksandr R.

It's potentially useful in compiled code, given that one can't Return[val, fun] inside the VM. Daniel also claims to have productively used Goto; he seems to get more mileage than most out of the procedural constructs.

I don't recall that I've ever needed them, though. On the other hand, I never used a For loop in anger either.

R.M

I'm always impressed by how much Daniel and Leonid get out of procedural code... I've sort of forced myself to avoid that line of thinking when it comes to mma, so I'm routinely reminded to not be close minded.

Oleksandr R.

@R.M I find the paradigm rather clumsy and hard to understand, but it has an undeniable utility in compiled code, which IIRC is mainly why Leonid uses it. I'm perpetually amazed by Daniel's procedural masterpieces, though.

R.M

2:52 AM

I beat you by 20 seconds! I'm excited. — s0rce 45 mins ago

A lot of people are happy about it... lol. That comment has more upvotes than either answers

J. M.

I tend to switch to procedural in "back against the wall" situations (except the cases where procedural is the only way to do things in language X).

@R.M Small joys. ;)

R.M

@J.M. I'm happy that me being slow made someone happy :) I'm always thrilled when Mr.Wizard isn't around :D

rcollyer

3:12 AM

@R.M I love beating him or Leonid to the punch. But, I'll settle for beating you, JM, or any of the other top users, too. :)

R.M

@rcollyer Apparently, I have a much better rate of being first... 39 enlightened to his 23 :)

Well, this is first and 10 upvotes, so the true number might be different

J. M.

@rcollyer The appeal of being "Quick Draw Robert" is a bit hard to resist, I suppose... ;)

belisarius

0

Q: Solving this in mathematic?

I have following code in mathematica: rbar = 0.006236 rt = r_bar k = 0.95 sigmar = 0.002 betazr = -0.00014 sigmaz = 0.4 pi = 0.99 chi = 0.05 Cbar = -3.7 alpha1[n_] := alpha1[n] = alpha1[n - 1] + alpha2[n - 1] alpha2[n_] := alpha2[n] = k (alpha2[n - 1]) sigma1sq[n_] := sigma1sq[n] = sigma2sq[n...

R.M

@belisarius what about it?

J. M.

@belisarius Oh joy. Not even a problem background...

belisarius

3:25 AM

@R.M I was just "tweeting" it here for you

@J.M. yeah, seems too convoluted to be true

Sounds like some stats physics going on

Or he is calculating the volume of a flock of elephants. I really don't know.

R.M

That should be a standard comment to such questions... "What error do you get when you try to integrate one elephant"?

belisarius

@R.M yo momma's integrable only from "0" to "elephant-divergence"

J. M.

"Yo momma's so fat, she can cover up Gabriel's horn..."

R.M

3:41 AM

Yo momma's so fat, the compiler implements an infinite loop by going around her waist

belisarius

Yo momma's so fat that yo poppa ... no, forget it

rcollyer

@J.M. Yeah, but it doesn't come off as a good cowboy name ...

@belisarius painful, just painful.

Definitely a candidate for migration ... to the delete pile.

belisarius

@rcollyer ha! yes ...

R.M

if it is stinky, flag on Stack Overflow to not migrate :)

belisarius

@R.M Yeah, go and say in SO: "we don't want to solve the thesis problem for anyone"

rcollyer

3:55 AM

There are ways to improve it ... and no I'm not going to.

Night.

belisarius

Many people think they can come to a Q&A site and ask "How should I calculate my thesis' integral". And they think a bunch of idiots will work a week in solving his problem

@J.M. I was once in a conference by this guy

Luis Santaló

Luís Antoni Santaló Sors (October 9, 1911 – November 22, 2001) was a Spanish mathematician. He graduated from the University of Madrid and he studied at the University of Hamburg, where he received his Ph.D. in 1936. His advisor was Wilhelm Blaschke. Because of the Spanish Civil War, he moved to Argentina where he became a very famous mathematician. He studied integral geometry and many other topics of mathematics and science. He worked as a teacher in the National University of the Littoral, National University of La Plata and University of Buenos Aires. Works Luis Santaló published...

who was talking about the history of the Gabriel's horn problem

very very interesting

F'x

8:06 AM

@J.M. @SjoerdC.deVries hi mods, do you think this Meta Q can get featured to help start the discussion?

4

Q: Could Mathematica.SE hold a mini-contest?

Edited now that the site has graduated: How do you feel about holding a Mathematica mini-contest? It seems to me that this is a great fit to our community’s overall “we find plenty of ways to do stuff” spirit, and it could help publicize our site in an effective manner. I'd be willing to step up...

discussion site-promotion

we don't have much meta activity, and I'd think this could be a great way of publicizing the website in a good way (by which I mean, not attracting more “what's wrong with this code?” questions)

Sjoerd C. de Vries

8:32 AM

@F'x Done,but could you be a little more specific about your ideas wrt contests in your post? Not much time for discussion now, sorry.

F'x

@SjoerdC.deVries thanks… I wanted to get the general feeling about the idea itself, rather than propose something too specific. But I'll try to add a little

Rolf Mertig

10:21 AM

@R.M Thanx! And performance-wise, which function is better in your experience? Or is ListConvolve using Fourier and InverseFourier anyway under the hood?

@J.M. Recently I had to implement a somewhat tricky Monte-Carlo algorithm and the most readable (and closest to the paper) way of implementation in M was to use Label and Goto. It was the first time I saw no obvious alternative. In 22 years of Mathematica programming ...

J. M.

10:53 AM

@RolfMertig Okay, I'll take that example... :)

@F'x Yeah, it'd be nice to bring up something more concrete so we'd have something to talk about. ;)

Rolf Mertig

@J.M. Regarding For loops: Obviously Do is more M-like, but if you have a long loop, I find it easier to read at the beginning of For[ ... from where to where to loop runs. So it all depends and I think readability (also for non-M-freaks) should be more emphasized, in general.

J. M.

@RolfMertig Yes, they use FFT...

@RolfMertig Hmm, yes, that's another defensible use of For[], but the first thing I'd consider is if I can split off sections of the body as separate routines... basically, For[] only if "back against the wall". :)

Rolf Mertig

@J.M. Thank's. I'll check it with my problem nevertheless. You never know if what is written is true in Version x ...

J. M.

@RolfMertig Oh, certainly; testing is a must. FWIW, I'm not even sure if they use FFTW under the hood...

Rolf Mertig

@J.M. I think Do should have been really like SetAttributes[DO,HoldAll]; DO[iters__List, expr_] := Do[expr, iters];

J. M.

11:03 AM

@RolfMertig I suppose one could make similar arguments for Table[], Sum[], Plot[]...

J. M.

11:14 AM

...so yes: "why are the iterators the last arguments?" is a good question. :)

Rolf Mertig

@J.M. But there is only one person on earth who could answer that question and even change it. But he will not. So, no, let us not ask questions about language design (like why is a comment not a Mathematica expression, or why is there no useful non-commutative algebra built-in to Mathematica, etc. )

J. M.

11:31 AM

Oh, well.

belisarius

1:22 PM

3

Q: Is migration a potential rep Black Hole?

Today I asked for (and was granted) migration for a question from SO to Mathematica.SE When the migration was done I lost some rep on SO, and as I've already capped at the destination site that rep was not gained there. Nothing serious, just a few points. But I wonder if the same could happ...

discussion reputation migration

JFYI

R.M

@bel you did get rep for that. If you go to your rep tab and check, there's an entry for dec' 10

belisarius

@R.M really? let me see

@R.M yep ...

blush :)

question deleted

was a dup

R.M

1:51 PM

:)

belisarius

@R.M Now I have rep gained in this site before the site started. Tell me about "the arrow of time"

R.M

Heh, many users do... If you check "year" and "all time", the difference is the transferred rep... Almost

belisarius

2:08 PM

damn repcap

Rolf Mertig

2:45 PM

Slightly simpler: {a, b} = RandomReal[1, {2, 31}];
Total[Chop[(ListConvolve[a, b, {1, -1}, 0]) -
With[{len = Length[a] + Length[b] - 1},
Sqrt[len] InverseFourier[
Fourier[PadRight[a, len]] Fourier[PadRight[b, len]]]]]] === 0

belisarius

6:23 PM

@GraceNote You here?

I have a q about mod nominations

Grace Note

Oooh, nice, a question about it. Fire away

belisarius

@GraceNote Hi! We have a nominee for the oncoming election, but he lacks the experience for the job. I wonder if the nomination process does not filter candidates in some way. I don't like the idea of him being hurt. His intentions are (of course) good.

R.M

I was wondering about that too... Stack Overflow nominations require deputy, strunk & white, higher rep threshold among few others

Grace Note

@belisarius Yes, I noticed that there's so far only one nominee, which is actually more concerning to me than this one's lack of experience

@R.M The site is too small and young for us to set the same kind of barriers we put on Stack Overflow. Which we also do because they tend to get over thirty applicants.

belisarius

@GraceNote No, I think more people are going to engage in a couple of days. The community is very participative

R.M

6:31 PM

@GraceNote I'm actually glad that people are taking the time to consider rather than mindlessly rushing to nominate themselves like on SO.

belisarius

yep

We know each other quite well now. I know we are not going to trash the election

R.M

exactly

Grace Note

@belisarius It is participative, which is why I expected at least murmurs. Maybe I've been missing the murmurs, then

We were internally thinking "Maybe people are just working on their nomination speeches", but for the most part it came across as silence, which is eerie to say the least

belisarius

No, no murmurs. We really don't need "speeches". There are at least 20 users we know are able to do the job quite well. But evrybody considers it a job, not a privilege, as it happens sometimes in other sites

5

Grace Note

So, people are thinking about running, though. Heavy emphasis on the thinking, but they are thinking

Back to the current nominee - I think Verbelia's approach in the comments was a decent way to start it - if you have concerns about one's experience, it's better to let them know and help them shape up. If this user seriously considers this an option, then it would be wiser to help them understand what they need to do to be considered by the community as an option, than to cut him off by imposing a mechanical restriction

R.M

6:40 PM

We won't be, if we don't think.

Tim Stone

The solution of course is to have Hypnotoad "persuade" everyone into action.

belisarius

@TimStone That is a last resource. We don't want legal trouble

Grace Note

I'm pretty sure Hypnotoad is a solution to legal trouble

belisarius

@GraceNote Well, he's more toad than hypno ...

Anyway, I'll go and try to convince the nominee to rethink.

Thanks for your time!

R.M

Tim Stone

6:51 PM

:D

hypNOtoad

:)

7:35 PM

@GraceNote I, for one, haven't stepped in yet for a number of reasons. First, having had the privilege for the first half year I wouldn't stand in the way of ambitious, new mods. This is a nice gang we have and if someone else wants to try, by all means, go!

Second, the workload is not so high as on SO for instance, but the pressure you feel to spend at least an hour per day on the site, spread over various check-ins is having an effect. Mathematica.SE is addictive and being a mod doesn't allow you to step back once in a while although it would oftentimes be advisable to do so career- and family-wise. So, I was thinking to let my own nomination depend on what else happens during the nomination phase.

I won't let this fantastic site go down, and will step in for sure if need be, but I' m not sure I' ll do it if there are already sufficiently qualified candidates. My guess (and fear) is that many potentials are reasoning along this line.

Grace Note

@SjoerdC.deVries So, in summary, you're holding off until you see not enough candidates are nominating

Sjoerd C. de Vries

@GraceNote That's the bottomline, indeed.

Grace Note

Okay, that's respectable.

I just hope not everyone has the same thought pattern, leading to a flood of nominations at the last minute, haha.

Sjoerd C. de Vries

@GraceNote That's precisely what I think will happen.

Grace Note

Heh

Sjoerd C. de Vries

7:40 PM

@GraceNote But anyway, no worries. I'm 100% sure we'll have a good team in the end.

Grace Note

No doubt about that. And even those who don't get elected, still can contribute to help keep run this place the same they always have.

F'x

I think most regular users (aka the community) will serisouly consider nominating… I don't know this community as much as the R.M, Sjoerd or belisarius (I'm not a regular on chat, and I have long "lurking only" periods), but it is a wonderful community

Grace Note

Having worked with various parts of the community for the blog as well as random general stuff, it definitely is a very solid community here.

F'x

it may be, however, that compared to other parts of SE, it is frequented by more busy/professional/otherwise-occupied types of users, which would lead to a higher barrier to people nominating

Sjoerd C. de Vries

True. We have to take care not to burn certain people. Szabolcs for instance, will be back in a couple of days/weeks, but he has been doing so much in the past it became almost unhealthy. His voluntary suspension springs to mind. Better not ask him, or we risk he agrees.

F'x

7:48 PM

@SjoerdC.deVries do you (as current mod) feel that the workload is too large to spread to three mods only?

belisarius

@F'x Well, Mr.wizard is Legion

Sjoerd C. de Vries

8:01 PM

@F'x Sorry, was on the phone. I can post the mod statistics, but this might not be advocated. I can say we get on average 1 or 2 flags per days, but we edit and comment like hell, roughly 1300 edits among us three and 3000 comments,

@F'x I would love to have a team of 6 mods, not sure whether that's feasible. But I can't really see how that could be a problem.

Hi @DavidZaslavsky

R.M

@SjoerdC.deVries I think they have annual elections

or roughly annual

Sjoerd C. de Vries

@R.M 'they'?

R.M

SE

F'x

@R.M no, elections happen “when needed”

R.M

it's based on demand too

Sjoerd C. de Vries

8:11 PM

@R.M but how does that relate to the number of mods?

Tim Stone

@GraceNote Yeah, for Town Hall planning purposes it is nice if it's known in advance that there will indeed be enough candidates for a Town Hall, heh.

R.M

@SjoerdC.deVries new election, more mods

F'x

@R.M only if needed

if the mods are happy about the workload and the SE team is happy about the moderation, no new elections happen

R.M

@F'x there won't be a new election if not needed, so nothing wrong in claiming more mods if there's a new election (unless someone has left)

F'x

see gamedev for an example of that

Sjoerd C. de Vries

8:12 PM

@TimStone Hi Tim, paradoxically it might be easier to fill the hall if it gets bigger

R.M

@SjoerdC.deVries Do you know if Mr.Wizard's planning on running? Haven't seen him around lately...

Grace Note

We evaluate once a year, or we run on immediate demand

@R.M He's out for a period of time

Sjoerd C. de Vries

@R.M He announced he was going to slack a bit

R.M

gotta close up that 6k gap then... :D

Sjoerd C. de Vries

We have worked for a couple of months without J.M. too. It's manageable with two, but it's getting a bit stressful

belisarius

8:17 PM

@SjoerdC.deVries I think there is no need to get stressed. If three mods are needed to run the site, we should have four

4

Sjoerd C. de Vries

@R.M I guess, we all have a wait and see attitude on this.

F'x

@belisarius yeah… we're worth four mods :)

belisarius

@F'x I mean, we are mostly working or advanced uni students. It's natural that time is a precious thing for us. And pressure is no good ...

Sjoerd C. de Vries

@GraceNote How about increasing the number of mods? It might be easier to get the busy folks interested in a part-time mod job.

Stack Exchange

1

Q: Can/should we have additional reasons for closing?

Now that the site has graduated, it is attracting a lot more attention from newcomers to Mathematica, as well as frequently receiving migrations from StackOverflow. I suppose I don't have to point out to anyone that some of these questions provide limited evidence of sincere effort on the part of...

discussion feature-request

David Zaslavsky

8:25 PM

@SjoerdC.deVries hi

Sjoerd C. de Vries

@DavidZaslavsky Have you been eying the election page?

David Zaslavsky

@SjoerdC.deVries not particularly

I haven't had time to be active on the site for a while

Sjoerd C. de Vries

I noticed. Physics.SE busy or your day job?

David Zaslavsky

Both, but more so the day job

Grace Note

@SjoerdC.deVries We sometimes up the number but I'm not sure that we particularly need more

F'x

8:31 PM

hum, that “general reference” meta Q by Oleksandr is bound to generate some debate… at least it did when English introduced it a while back

David Zaslavsky

Pretty much anything that gets changed will generate debate

Sjoerd C. de Vries

@F'x I don't see a reason why you shouldn't do it. As long as the list of close reasons fits on a single screen it should be ok.

F'x

@SjoerdC.deVries there have been arguments against it (and it's not used on many SE sites)… one of them is that you hope that the Q&A site itself becomes a standard reference at some point, which doesn't happen if you don't allow these questions

Grace Note

@SjoerdC.deVries The issue is less on the "decide which close reason to use" mechanical end

F'x

Chemistry.SE has taken another path: some of these are “not real questions” (it's not a question if you can't formulate it coherently and don't even know where to begin looking), the others should be answered once, and later closed as duplicates

Grace Note

8:39 PM

A simple option, if "Not a real question" doesn't fit from whatever vagueries are present, is to solidly define what realm of questions you'd say don't belong, and make them off-topic.

belisarius

@GraceNote I think the problem is that we are mainly speaking of "too simple" questions. And that is always "too subjective"

Grace Note

@belisarius Having a close reason that equately says "This is too simple for us" won't solve that problem, though

F'x

@GraceNote I don't like that one much… if a newcomer asks “What is the Mathematica command to make a 3D plot?” on Mathematica SE and you tell them “This question is off-topic”, they will most likely not understand it

Grace Note

@F'x Will they really understand it any further if we have a close reason that says "You could find the answer elsewhere, why are you checking on Mathematica.SE?"?

R.M

@GraceNote There are some questions which are technically RTFM, but the necessary detail is in an almost hidden corner of the manual that the question is worth having as an entry point. Then there are others that are plain lazy and the answer can be found by simply typing two words from the title into the help menu (e.g. "How do I total elements in a list")... The latter one is what we don't want, but none of the close reasons fit it well.

We've been using TL to close these, but a "general reference" reason would be better.

Grace Note

8:43 PM

@R.M General Reference isn't one that'll fit it, though, not very well at all

R.M

@GraceNote why do you think it won't fit? I think it certainly does

Grace Note

Let me get someone who can explain this better...

F'x

@GraceNote we're being escalated to “level 2 SE sales team” :)

Grace Note

@F'x It's not quite escalation, more of a side pass

Mostly because we had just discussed this hours ago and he had some very nice ways of phrasing it that I didn't write down word-for-word so I can't quite replicate it

belisarius

"phrasing it" ... like "go ask yo momma"

F'x

8:47 PM

well, I'm gonna escalate this issue to my bed… but I'm interested, so I'll sure read the transcript to check for the phrasing

belisarius

nigths!

R.M

@belisarius "Yo momma's so huge, you can close anything as a general reference of her"

belisarius

@R.M good one !

Brett Champion

9:23 PM

Quick plug that we're having another Virtual Conference in a couple weeks. Vitaliy put up an ad for it.

belisarius

@BrettChampion upvoted that. Thanks!

R.M

@BrettChampion Looks like the previous virtual conferences were a big hit... this one's longer and 2 sessions too! :)

Brett Champion

9:41 PM

@R.M I suspect you're thinking of the 'Experts Live' events. The previous Virtual Conference was larger. (And, for one of the sessions, involved me coming into the office early in the morning, then going home and getting some more sleep.)

R.M

Ohh... right. I didn't notice that they were different :D

belisarius

10:23 PM

@BrettChampion Now it's Vitaliy turn, I see

belisarius

10:33 PM

Mmm .. no V9

R.M

10:44 PM

@OleksandrR. You can't shy away from asking your first question ever by asking one on meta instead ;)

Oleksandr R.

@R.M I thought that one was more pressing as there has been a lot of closing lately. :)

belisarius

@R.M We should confabulate to close @OleksandrR first question as "covered in standard sources" (aka RTFM) ... Ops he is here :)

R.M

Closed as "Ask Oleksandr"

2

belisarius

starred!

Oleksandr R.

11:22 PM

Haha. :) I was just digesting Leonid's latest epic... if it's true that data structures make the program, and facility with them, the programmer... well, I'll have to study hard if I want to become half as good a programmer as he is.

R.M

His answer to the boggle question was what convinced me that data structures play a more important role (in larger applications) than programming smartly/neatly/cleverly/etc. A combination of both can be deadly

Transcript for