03:00 - 20:0020:00 - 00:00

3:37 AM
Any mod around?
piiiing
@J.M. JM?

@R.M Yeah, dammit

heh, out of 8 questions 5 are negative

he is asking the same again and again
perhaps he is helpless with maths ...

yes, he doesn't know how to generalize answers or to recognize a general answer

3:43 AM
perhaps he is blind

"Thanks for showing sin^2(x) +cos^2(x)=1... now, how do I find out the answer for x= pi/4"?

Grrrrrrrrr

Can you guys help me?

no :)

...
¬¬

3:44 AM
well, let's see
do you need money?

Everybody need money.

@Verde you mean, "do you have money?"...

Oh no...SCAMMERS!

so, if you do need money, go to lawyers.se
here, you are losing your time

R.M is one of those guys who plant that "stop watching porn and get laid" banners on porn sites.

3:47 AM
never saw a porn site, did you?

Me? Never.

good
?

I'm learning calculus, on a part of transformation of functions.

@GustavoBandeira A very rich man died and left no will... I'll give you 50% of his money held in Swiss accounts if you wire \$1000 immediately to me

f[c_] := Plot[(x^2 + c), {x, -7, 7}, AxesOrigin -> {0, 0}](*Up/Down*)
Table[f[c], {c, -30, 30, 20}] // TableForm

To obtain the vertical shift. But I have no idea on how to make the horizontal shift.
Bizarre... this girl reminds me of my mom. But my mom is white. 0.o

3:51 AM
@GustavoBandeira Try: `f[v_, h_: 0] := Plot[(x + h)^2 + v, {x, -7, 7}, AxesOrigin -> {0, 0}]`
`v` is for vertical and `h` is for horizontal

f[c_, a_] :=
Plot[((x - a)^2 + c), {x, -7, 7}, AxesOrigin -> {0, 0}](*Up/Down*)
Table[f[c, a], {c, -3, 3, 3}, {a, -4, 4, 4}] // TableForm

This is what I was trying to understand: (x + h)^2 + v
I didn't know where to insert the variable for the horizontal shift.

run my code
not RM's. Toad's code is contagious

get out!

3:57 AM
R.M. Code is scam!
Thanks for the help, guys.
I saw this in my book, but It wasn't so clear where I should input the variable for the horizontal shift.

wherever you find x, replace with x+c or x-c, as the case may be

This kinda reminds me of function composition.

you are welcome

no hablo español
"Fortified chocolate drink/food"?

@Verde Oh, youre from Argentina.

4:07 AM

I wondered: "How does he know Toddy?"

@GustavoBandeira :)

@GustavoBandeira Now hear THIS version youtube.com/watch?v=1QBQiJyb6No

Way better.

4:11 AM
This is the full one
very beautiful

Are you guys into modern music? Hear this.

@Verde When the music started, I thoght it was Vangelis' Chariots of Fire

@Verde that's the original artiste, right? Perón?

I guess it's the same note.

4:15 AM
@R.M Peron was a president. The singer is Nacha Guevara
the photos are peron's wife. Evita
@GustavoBandeira Can you understand a lyrics in Spanish?

@Verde Yep

@GustavoBandeira Ok. Let me search for it

@Verde ah, ok. thanks for clarifying!

verguenza = shame?

4:28 AM
@GustavoBandeira yep

0

I am relatively new to this site, and I have noticed a common abbreviation: MMA. What does the abbreviation MMA stand for? The abbreviation seems to be used frequently among senior members of this website. Searching via Google was not useful because of the more common usage in mixed martial arts.

@GustavoBandeira Where are you? Sao Pablo?

mma lol
@Verde Recife.

@GustavoBandeira nice!

Recife (, Reef) is the fifth-largest metropolitan area in Brazil with 4,136,506 inhabitants, the largest metropolitan area of the North/Northeast Regions, the 5th-largest metropolitan influence area in Brazil, and the capital and largest city of the state of Pernambuco. The population of the city proper was 1,536,934 in 2010. Recife is located where the Beberibe River meets the Capibaribe River to flow into the Atlantic Ocean. It is a major port on the Atlantic Ocean. Its name is an allusion to the coral reefs that are present by the city's shores. The many rivers, small islands and over...
I'm hearing the song.

4:34 AM
The song is nice, isn't it?

Yep
Were they trolling Evita?

Nooooooooo
Let me search for the lyrics

No, I understand the lyrics.
I just can't understand the context.
Guys:
0

I'm learning C and I kinda know how to program on Mathematica. On Mathematica, I can declare a variable simply by writing: a=9 a="b" a=9.5 And it seems that Mathematica understands naturally what kind of variable is this by simply reading and finding some kind of pattern on it. (Int, char, fl...

In computer science and computer programming, a type system is said to feature strong typing when it specifies one or more restrictions on how operations involving values of different data types can be intermixed. The opposite of strong typing is weak typing. Interpretation Most generally, "strong typing" implies that the programming language places severe restrictions on the intermixing that is permitted to occur, preventing the compiling or running of source code which uses data in what is considered to be an invalid way. For instance, an addition operation may not allow to add an in...
far easier to perform compile time optimizations, among other things

Yep. I thought there was some kind of tradeoff.

4:41 AM
@GustavoBandeira The lyric's author was ´Pedro Orgambide. A wonderful writer. And peronist. The song displays the tension among Evita and the Argentine aristocracy

`variables` is a small tag (and a meta tag at that)... it'll probably never get any attention. If you tag it `C`, you'll be eaten alive... your call :)

Added C, Python and Mathematica. As I mention them in the question, I guess it's going to be better.
Is mathematica more famous than MatLAb?
And more used?

@GustavoBandeira get a shovel ready and start digging 6 ft deep
3

@R.M Yep, I remeber my last question. It was so naive, I thought it wouldn't attact all this.
attract
@Verde Now I have a context.

@GustavoBandeira O my! You shouldn't!

4:47 AM
@Verde ?

This is an example of why I dislike people making tiny, inconsequential and incremental edits without fixing all of it at once... it is understandable if that's the only thing that needed fixing

@R.M starred

5 monkeys edit it a bit at a time and kick it to CW
2

@Verde Where should I ask then?

4:49 AM
@GustavoBandeira Here :)

As It involved more programming languanges, I thought It would be adequate to do it there.

@GustavoBandeira By "here" I mean "in this chat"

ah, yes.

Oh, ok.

4:51 AM
@R.M :P

@GustavoBandeira btw, I should've linked to static typing, not strong typing for that... can't change now

Now a top C++ developer will come and collect 10^6 rep points by explaining static types
@R.M Do you have a reddit account?

@Verde those damn gold diggers... now, if only it were about something something random and CLT...

@Verde Is there a problem on this?

@R.M or QCD

4:55 AM
@Verde yeah, sort of

@GustavoBandeira Well, you are asking a question that was debated in the academic and programming communities for years in a naive way. Perhaps they will treat you with love

@Verde Oh, was compeltely unaware of this.

@GustavoBandeira The problem is really subtle and has many, many edges

@Verde should I use vim or emacs?

vim
or emacs

4:58 AM
Should I delete the question?

@GustavoBandeira probably too late now

@GustavoBandeira I think you will get at least one good answer. But do yourself a favor, edit the question and ask for references
many good books and articles will come through

I noticed that, but as I'm not in a formal C.S. course, I couldn't discover what was the name of this.

@GustavoBandeira Typing
strong, lazy, dynamic, static, many flavors

@Verde I just don't know what should I change.

5:03 AM
@GustavoBandeira Just add a final question
Can you provide me with pointers to some articles/books to understand this?

I added: "References on the topic are going to be very useful. Thanks."

or something like that
@GustavoBandeira OK

@GustavoBandeira I'm waiting for someone to link you to the wiki article on typing... :) It's fairly comprehensive, at least for what you want to know

At least you don't tagged it as C++. Those are the real wolves

do it!

5:06 AM
@GustavoBandeira Anyway, let me show you an example of the problems that arise in Mma because it typeless nature
Try
for example
s = DSolve[{y[x] == y'[x] && y[0] == 1, y'[0] == 1}, y, x]
Plot[y[x] /. s, {x, 0, 1}]
s1 = DSolve[{y[x] == y'[x] && y[0] == 0, y'[0] == 1}, y, x]
Plot[y[x] /. s1, {x, 0, 1}]

Done.
"DSolve::bvnul: For some branches of the general solution, the given boundary conditions lead to an empty solution."

@GustavoBandeira Now try to prevent that error

== 1?
But I guess that doing so wouldn't be the solution.

no no ... I mean: a runtime error is a bad thing. Try to think a way so that the program can manage the error situation and degrades gracefully

5:22 AM
I cant.
You can proceed with your reasoning.
I guess you're trying to reach a conclusion with parameters I'm unaware about.

Quiet[s1 = DSolve[{y[x] == y'[x] && y[0] == 0, y'[0] == 1}, y, x]]
If[s1 != {}, Plot[y[x] /. s1, {x, 0, 1}]]
but ... it is awful
those are the disadvantages of typeless languages
Note: Mma isn't really typeless ... I'm being a bit informal here

I'm seeing the changes in the code. But I don't know what they mean in that context.

Ok. It's not easy. Let's try another example
a = 1; b = {};
a + b
Makes sense?

I understand it. It's a sum of a number plus an empty set.
Empty list*

In a typed language, the compiler should insult me
the sum does not make sense

5:31 AM
I've read somewhere that this is a feature of new programming languanges.
You can sum a number plus a string. - The compiler tries to evaluate it.

@GustavoBandeira the Ford model "T" had a "feature" . It ate gasoline for breakfast.

So, if this is an analogy, this feature makes the programming languange being slow, right?
But, if this feature is there, it must have a positive point, isn't it? I just can't see why one would like to sum a number with a string.

@GustavoBandeira It isn't just about performance. You need to be aware that programming is a business with many faces. If you need to solve an ODE for your thesis, your requirements are not the same than those needed to manage air traffic at a crowded airport. You don't want a plane crash because someone forgot to set the return variable from some rarely used function to `0` instead of `{}`

So, in a weak typed languange, there is more probability of bugs?

@GustavoBandeira I'd rather say that there is more responsibility on the programmer's side
but wait ... the debate is a real and deep one. It can't be solved in a few lines :)

5:42 AM
What you mean?

Sorry, gotta go. It's late there too :)

Oky
I'm gonna sleep too.
Cya.
Thanks for the information.

6:22 AM
@J.M thanks. I can anticipate an efficiency issue as on my mac the ContourPlot3D routine is quite slow (but may be its an opengl rendering issue). I ll try it and post it.

4 hours later…
10:08 AM
@GustavoBandeira no just sit back and laugh if they start snapping at each other

Not that I'm complaining or anything, but I am a little surprised that this answer got 10 upvotes. It might be a nice canonical answer but I won't pretend it was difficult to answer if one has the domain knowledge. I just had the luck of having my lunchbreak at the right moment.

@Verbeia it's not unusual for this to happen. also, it's a well-written and comprehensive answer, so why not?

@acl I guess so, but I admit I got a surprise when I came home just now and logged on - 11 upvotes now!

3 hours later…
12:59 PM
@Verbeia Democracy also works that way. Sometimes, surprisingly, the good guys win.

1:49 PM
@J.M. I wonder why Mma graphics internals don't use standard gradients. Perhaps just historical reasons ... `ColorData[]` was introduced in v6

2:08 PM
People ask odd questions on MathGroup. The other day people asked about C compilers and the Savitzky-Golay filter, both of which I've posted more than once about in the last 6 months (essentially giving the answers they were looking for). Both posters also claimed that they searched before posting... hopeless.

2:35 PM
@acl lol

@OleksandrR. People ask odd questions everywhere

549

I can't get my head around this, which is more random? rand() OR rand() * rand() IÂ´m finding it a real brain teaser, could you help me out? EDIT: Intuitively I know that the mathematical answer will be that they are equally random, but I can't help but think that if you "run the random nu...

Yeah, I was also trying to know about the torn function.

@GustavoBandeira Yep, my most voted answer

@OleksandrR., yes, the C compiler question on Mathgroup is strange. After all gcc has been around for 500 years :) it is free and all. I think some people never heared of google search.

2:44 PM

@GustavoBandeira because it comes from xkcd.com A wonderful site
@GustavoBandeira Anyway it was turned into community wiki, so no rep points for the "author"

But it's a joke and a naive answer based on "I think P is true because I think it's true".
I gave a naive answer one time and no one gave me 100 upvotes. ¬¬

@GustavoBandeira But that question was linked in reddit several times. So it got a lot of views

@Verde I wish I knew, too...

@GustavoBandeira Also, my answer shows only VERY basic stats knowledge. Does not deserve 1K upvotes, surely

3:02 PM
@J.M. that would be nice, if you have time. I for one would be keen to see your approach, especially for the endpoint coefficients for the derivatives.
I'll post my (more naive, matrix based) code too if you do such a question, just for comparison's sake.
Also, chances are, the question will then become top hit on Google for "Mathematica Savitzky-Golay", which is good, because all the public code I found is crap.
@NasserM.Abbasi gcc on 64-bit Windows is not completely straightforward. I wrote about it, though, so it should not be beyond the wit of man to find the information that's already out there...

@OleksandrR. Ok, but I did not see in the compiler question that they asked for 64 bit? They said they just looking for C compiler for windows 7. One can run 32 bit on windows. gcc can run in cygwin under windows, also mingw on windows.

@Verde Hmm. I actually don't consider this a problem--or at least not for a term-rewriting language. Who knows how the term will be rewritten subsequently? If certain terms represent errors in a given context, that is different from a problem with the language IMO.
@NasserM.Abbasi yes, but running 32-bit Mathematica on 64-bit Windows is undocumented. I agree that you can do it, but I wouldn't consider it a better solution than just using the 64-bit compiler.

3:24 PM
@OleksandrR. I do believe I remember giving you the routine for the smoothing coefficients here... or am I misremembering?

@J.M. you only showed a small part of it, for the central section (not the endpoints).

@OleksandrR. Olek, you know, the typed vs non typed arguments are infinite. The outcome is always: it depends on what you are trying to do

@OleksandrR. Hmm, I see. I'll have to think about how to formulate the post, then...

@Verde yes, I think you're right. Of course, if you design your language around the principle of "do what I meant"... well, you get perl. ;)

@OleksandrR. An that is why perl is both loved and hated :)

3:30 PM
@Verde ...it has to be emphasized that it's "and", not "or". ;)

@J.M. Yeah. It's AND

I admit I prefer Python (not that I know perl really; I just looked at a little bit of code and found it mostly senseless and so decided not to proceed any further). But that argument is a holy war in itself. One dynamic language that I think nobody loves: PHP. A friend of mine is PHP programmer and hates every single minute of it; he loathes the language with a passion.

Well, PHP is a bit like trying to make a platypus by grafting a duck's bill onto a beaver...

@OleksandrR. languages and paradigms wars are mostly a cliche. Use the tool for what is does nicely. Have several tools in your bag. Forget the arguments.

@Verde indeed, language agnosticism is a good thing. Know the algorithms. Pick the language that best illustrates your algorithm for the task at hand.
On another note: I like regexes, but I've come to understand why most people's eyes glaze over when they see them...

3:43 PM
@J.M. Once upon a time I migrated a full core banking system with regexes.

@Verde well, I'm not a language snob, really. I even used to use BASIC for a while! And I agree with you that it's best to use whatever is best suited for the task. Perhaps I was wrong to make a judgment between perl and Python based mainly on looking at the examples in "Higher Order Perl" (which is sometimes touted as an example of the wonders one can accomplish with perl). On the other hand, Python looks lame as well until you notice numpy and itertools.

@Verde *I* am not surprised at all... ;)

@OleksandrR. And then you have java :)

@OleksandrR. (On a passing note, the author of that book is quite active in math.SE...)

@J.M. I have no problem with the content of the book. But perl doesn't seem like a good setting for those concepts; everything looked to me to be rather awkward and unnatural.
@Verde Java is probably okay if you like the procedural and object oriented paradigms. I'm not too keen on them personally, but a lot of people are. And as Leonid says, Java has a great library and a fast VM. You could use Scala or Clojure instead of Java, I suppose.

3:53 PM
@OleksandrR. Java is a shame on OO features. It was designed as a toy project that grew out too many tentacles.

@J.M. arguably the audience is people who already know perl and want some examples of how to use it for functional programming, not people who know about functional programming and want to see if perl is any good for it. So I was in the wrong camp to begin with.

@OleksandrR. ah, that point I cannot argue with... :)
@Verde Makes you think... PHP and Java got popular despite being Rube Goldbergs.
(I don't want to think it was because of...)

@J.M. language popularity (as popularity in general) is linked causally to many things. Rationality being very south on the list

@Verde I am not sure, but hasn't Java improved significantly in recent times? It isn't Smalltalk, but at least it supports generics and reflection now.

@Verde I know, I know, "real life doesn't have to make sense" and all that...

4:01 PM
@OleksandrR. Java supports "almost" everything now. You can build up layer over layer of features and behaviors. Ada was the same since its inception.
But ... that is a problem, not a virtue

Ada is basically a highly simplified version of ALGOL 68 with design-by-contract, isn't it? I admit I know nothing of Ada 95.

@OleksandrR. Ada is "extendable". You could write COBOL in Ada if you want

For some reason this conversation got me thinking of Knuth's "man or boy test".
From here:
```    \$RecursionLimit = 1665; (* anything less fails for k0 = 10 *)

a[k0_, x1_, x2_, x3_, x4_, x5_] := Module[{k, b },
k = k0;
b = (k--; a[k, b, x1, x2, x3, x4]) &;
If[k <= 0, x4[] + x5[], b[]]]

a[10, 1 &, -1 &, -1 &, 1 &, 0 &] (* => -67 *)```
It seems like cheating to do this in an interpreted language...

5:10 PM
@OleksandrR. Do you know Eiffel?

3

As a thank you for being awesome, if you are on page 1 or page 2 of … http://mathematica.stackexchange.com/users?tab=reputation&filter=all … we'll be sending you a little care package shortly: Mathematica t-shirt in your size Mathematica die-cut, vinyl stickers Stack Exchang...

@Verde No, I don't. (Actually I mixed up Eiffel and Erlang in my head when you mentioned it; that shows you how much I know about it...)

when you have some spare time ...
In fact all books from Meyer are jewels

The languages on my current "to learn one day" list are C++, Prolog/Mercury, possibly Clean, Maude... I admit I am not a great fan of the object oriented paradigm although I concede it has its uses. Maybe Eiffel is the language to make me love it?

5:28 PM
@OleksandrR. It was for me

5:49 PM
Anyone willing to offer one more close vote on this one?
0

Possible duplicate: Using FindFit to find an exponential function \$a\,b^t\$ I have a lengthy function with 6 fitting parameters. When I tried to use FindFit[data, function, {parameters}, var] the following error occurred: FindFit::nrlnum: The function value {-0.486377 + 0.0275527 I,-...

Thanks @J.M.!

@OleksandrR. I don't think Eiffel is going to enter mainstream. Think of it as a learning experiment (and manage your reading schedule accordingly)

@Verde yes, I gathered as much. The same is true of Clean and Maude (both are research languages). Pure might be a more mainstream alternative to Maude, I suppose, and Haskell over Clean. But that is a very relative definition of "mainstream"...

@OleksandrR. :)
We should obliterate this one
0

Haha, This question turns out to be a elementary mistake, what a funny and annoying resultâ€¦ â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€”â€” I still use the one-dimensional heat conduction equation as the example. Here is the code: a = NDSolve[{D[tes[t, x], t] == D[tes[t, x], x, x], tes[t, 0] == t, tes[t, 1] == 0, tes[0, x] =...

6:07 PM
Voted TL.

Evening

Hello!

@Rojo hi

Hi Oleksandr, acl :)

@Rojo Ok. I am not greeting you either

6:13 PM
@Verde I did Verde/:hello but you were too deep in the room stack to be found

@Rojo That reminds me of a recent question :)
@Rojo `fec1 /: Integrate[fec1[x_] fec[x_], x_] := Intfec1[x];`

@Verde What was the question?

1

I am answering you, voting to close your question, and flagging it. I answered this for you at least two times before, and other users did that too. You should at least read the answers to your questions. fec1 /: Integrate[fec1[x_], x_] := Intfec1[x]; fe1 /: Integrate[fe1[x_], x_] := Intfe...

I see

6:28 PM
btw, for users <10k that lost access to the close vote queue in the `/tools` section when we graduated, you can also find it at mathematica.stackexchange.com/review-beta/close

@R.M You should make an add with that "Wanna close? Follow me!"

@R.M thank you! Was looking for that.

@R.M alternatively you could vote us back up over 10k

:D
:D

I don't think this is a duplicate of this at all

6:33 PM
@acl You are going over 10K before pentagons are allowed again in common speech

@acl agreed and voted as such.

@acl I voted "not a clue"

although I have a hard time imagining any way of answering it other than "you can't do that"
also, what's with the flood of questions on numerically solving the diffusion and inviscid flow equations?
@OleksandrR. (then again the person asking that question found the answers to the linked question very useful, which makes me wonder what is going on)

@Verde :D

Everyone start working on your rhetoric, elections are coming!
4

6:37 PM
Uh... something must've messed up my connection... I see two other :D from me

@J.M. @Verde and @chris thanks for the links to references on symplectic integrators, we've already implemented some simple examples and are now mounting our real attack

@acl You are welcome. First link is free.
@TimStone The kind of rhetoric we value here is more on the side of re-toric

@acl Questions like this can be indicative that a poster has gone down the apparent path of least resistance, without knowing that it's a dead end. Being told "you can't do that" and shown alternative approaches/related problems may be helpful in that case.

@TimStone Just look at JM's avatar

@TimStone haha! I got a caucus badge for an election that doesn't start until the 10th of Sept!

6:40 PM
@Verde Hah ;)

@TimStone just yesterday I was wondering if we were going to have elections! I don't want to be a moderator but it struck me that some of the current ones might be sick of it by now. :)

@Verde what do you mean by "Could we have a pentagon in the inside?"

Damn ... we have a problem. I don't know if there is anybody around fulfilling the mod's requirements: shows respect for their fellow community members in their actions and words

@Verde "patient and fair"

Sort of like a bootleg version of the t-shirt

6:44 PM
@Jin A hidden hyperbolic pentagon, you know. In the t-shirt's tag, or something

ahh

@R.M Yeah, I guess that's not accounted for since that page isn't linked from anywhere on the site at the moment (so there's no particular reason you should know to go to it)

well i already sent the image files to the printshop

@Jin clap!

yeah i wanted the production to start asap, because i want to make sure the swag packages get made in time for the WRI conference

6:47 PM
@Jin I think the conference will bring a lot of new users here

@Verde agreed!

It is the best possible place to publicize

I'm also thinking about making some MMA.se site minicards to go with the top user package/conference swag as well.
cards are easier to pass out to friends/colleagues/classmates.
I've made some in the past, for selected SE sites
3

I'm in the process of creating generic site cards for SharePoint StackExchange community. I'd like to pick 3 interesting questions be featured on the one side (individually). The idea is that when we pass out these cards to people, the questions are so interesting that they'd be inclined to get ...

@Jin With QR Codes?

@Verde to be honest I'm not a fan of QR codes...
no one uses them.
(except for very selected techies, or japanese)

6:50 PM
@Jin (blush) I do ...

at least in the US, it's very gimmicky imo. also messes up overall design aesthetics
@Verde well... you should contribute to picturesofpeoplescanningqrcodes.tumblr.com :)

@Jin true... I thought I was being smart and inserted a QR code in a recent poster (academic) of mine, linking to my website and papers... Everyone commented on how it was a cool/smart/neat idea, but not a single person used it

@Verde I prefer CueCat bar codes

@Jin unleash your creativity. Or drink champagne

I'm drinking Scotch right now

6:54 PM
At 3:00 in the afternoon? :P

@TimStone time is just a label. i live a label-less life.

Your life must be so cool. I'm in the office now, so drinking would probably be frowned upon.

You can identify anything

working from home has its ups 'n downs... theoatmeal.com/comics/working_home

@TimStone aah, welcome to the internet, where one can jet ski at 9pm in the moonlight while drinking scotch and eating bacon while chatting via an iPhone. I'm on a horse
4

6:57 PM
^ story of my life

@Jin Yeah, they only let me work from home on Tuesday and Wednesday now, heathens!
@R.M I would have been more impressed if your hose was a unicorn.

@Jin I understand you deeply
http://mathematica.stackexchange.com/questions/18/where-can-i-find-examples-of-good-mathematica-programming-practice
http://mathematica.stackexchange.com/questions/809/how-can-one-find-undocumented-options-or-option-values-in-mathematica
http://mathematica.stackexchange.com/questions/1803/how-to-compile-effectively
http://mathematica.stackexchange.com/questions/559/what-are-the-use-cases-for-different-scoping-constructs

7:20 PM
@J.M I tried to implement your suggestion. I have the following problem. Starting from a 4x4x4 field, nn = 4;

u = GaussianRandomField[nn, 3, Function[k, Exp[-k^2/2]/k]] // Re;

uf = ListInterpolation[u];

fx = Function[{x, y, z}, D[uf[x, y, z], x] // Evaluate];
fy = Function[{x, y, z}, D[uf[x, y, z], y] // Evaluate];
fz = Function[{x, y, z}, D[uf[x, y, z], z] // Evaluate];

pl = ContourPlot3D[{fx[x, y, z], fy[x, y, z]}, {x, 1, nn}, {y, 1,
nn}, {z, 1, nn}, Contours -> {0}, ContourStyle -> Opacity[0],
I get 2059662 leafs!
Now its probably because of the tube command(?)
@J.M Could you please guide me through the line extraction process if you know how to do that?

@Verde good choices! I particularly like Leonid's answers on how to compile effectively and the use of different scoping constructs. They give a solid overview of general considerations that is obviously borne of practical experience without getting in to the nuts and bolts. Very appropriate for an audience of experienced Mathematica users.

@OleksandrR. @verde @jin while these examples are extremely good questions and very educational they might not be the best for flashy advertising. Shouldn't we aim for some eye candy too?

7:40 PM
http://mathematica.stackexchange.com/questions/3528/extract-values-for-viewmatrix-from-a-graphics3d
http://mathematica.stackexchange.com/questions/2334/how-to-create-word-clouds
http://mathematica.stackexchange.com/questions/8716/how-to-create-hedcut-style-images
http://mathematica.stackexchange.com/questions/8507/artistic-image-vectorization

A mixture of pizazz and seriousness is probably best. I suggest we merge your and Verde's list

@SjoerdC.deVries We may also tweak some titles "How to peel a marmalade jar label with Mma" comes to my mind

@Verde Absolutely true. We have to inform and tickle curiosity at the same time. Will Jin be asking a Meta or are we taking the lead here?

@SjoerdC.deVries I think Jin deadlines are too tight. Perhaps we should start rolling it and see if he can make good use of our selection

@verde @OleksandrR. If only we had an answer to this one. Now that would cause a surge.

7:52 PM
the undo?

65

The Mathematica Front End's built-in Undo command can only undo a single editing step. Has anyone implemented or seen implemented an efficient and comfortable multiple undo? I have in mind ideas such as, CellEventActions that keeps a stack in the cell context pushing the cell state every time ...

Ha
I guessed it

A free t-shirt for you

(bows)

clap-clap
@verde rojo was working on it?

7:54 PM
@SjoerdC.deVries Yeah, I got very busy lately however

@SjoerdC.deVries Yep, he made good progress, but the whole thing is very difficult. I was testing his job

@Verde I'd only suggest that we don't go overboard with tuning everything just for this conference...

@R.M It's just some housekeeping

Leonid had been suggesting in the past he had ideas on undo too

@Verde get your broom out and start sweeping ;)
That can happen only if the first vote was cast as a user and the second later as a mod (by the same user)

03:00 - 20:0020:00 - 00:00