Wolfram Mathematica

CHM

1:18 AM

Has anybody browsed the Biology beta?

rcollyer

1:35 AM

@CHM Maybe once. Anything interesting?

CHM

@rcollyer I'm deceived, actually. I've read a couple of questions where the answers were copy-pasted from Wikipedia.

rcollyer

@CHM that's not a good sign, for them.

CHM

Not at all.

rcollyer

Here's a problem that seems familiar:

0

Q: Trigonometric fit in Mathematica not working?

I am trying to curve fit some periodical experimental data, and discovered that the methods that work for curve-fitting to other functions do not work for trigonometric ones--at least--the way I am doing it. Here is my code: falseData = Table[{x, N[3*Sin[4*x]]}, {x, 10}]; model = a*Sin[b*x]; fi...

CHM

Mention MMA.SE?

As in "you should take a look in our stack, see if it's been answered before."

rcollyer

1:39 AM

Will do so. The question, now, is it worth flagging for migration.

I opted to vote to close after posting a link.

CHM

Sure

rcollyer

For reference:

6

Q: Problem with NonlinearModelFit

I'm having trouble with a non-linear fit: fit = NonlinearModelFit[data, y0 + A Sin[\[Pi] (x - xc)/w], {y0, xc, A, w}, x] where data has about 15 thousand points and looks like this: The data can be downloaded here. Mathematica gives the following adjusted parameters: {y0 -> 30.4428, ...

fitting

CHM

I don't have enough rep on SO to vote.

rcollyer

No, but the vast majority of the top users do.

CHM

hehe

won't be a problem then.

I've had problems with ParallelTable[] yesterday, it seemed to evaluate forever.

rcollyer

1:45 AM

not a bit.

@CHM not an area of expertise.

CHM

Oh, just mentioning in case there was an easy fix I wasn't aware of.

rcollyer

I wish. It's something I should learn. just like compile ... :P

CHM

Oh, yeah... Compile[] will definitely be something to learn.

I can't wait for MMA9. I'm more excited by that release than by Diablo 3's.

rcollyer

Here's my current puzzle: test[a: (_ | {__} )]:={a} functions as you expect, but changing it to test[a: (b_ | {__})] := {a} no longer does; test remains unevaluated.

CHM

Works for me.

rcollyer

1:51 AM

Seriously!?! have to drop my kernel, then.

test is still staying unevaluated for me.

CHM

Clear[test];
test[a : (_ | {__})] := {a};
test[123]

Out[19]= {123}

Clear[test];
test[a : (b_ | {__})] := {a};
test[123]

Out[22]= {123}

rcollyer

Ah, I didn't give the definition I was actually using: test[a : (b_ | {__}) .. ] := {a}

    Clear[test]
    test[a : ((b_ | {__}) ..) ] := {a}
    test[124, {4}]

    {124, {4}}
In[38]:= Clear[test]
test[a : ((b_ | {__}) ..) ] := {a}
test[124, 4]

Out[40]= test[124, 4]

In[41]:= Clear[test]
test[a : ((b_ | {__}) ..) ] := {a}
test[{124}, 4]

Out[43]= {{124}, 4}

It seems by naming b, I only get one of them which explains the problem I was having.

Even better:

In[50]:= Clear[test]
test[a : ((b_ | {__}) ..) ] := {a}
test[{124}, 4, {5}, 4]

Out[52]= {{124}, 4, {5}, 4}

CHM

In[32]:= Clear[test];
test[a : (b_ | {__} | ___) ..] := {a};
test[123, 4]

Out[34]= {123, 4}

But that's not very interesting :P

rcollyer

Nope, but this works:

In[53]:= Clear[test]
test[a : ((b__ | {__}) ..) ] := {a}
test[{124}, 4, {5}, 2]

Out[55]= {{124}, 4, {5}, 2}

CHM

Yes, just checked it with
In[41]:= Clear[test];
test[a : ((b__ | {__}) ..)] := {a};
test["ceci n'est pas une pipe", {}, 1, {E}]

Out[43]= {"ceci n'est pas une pipe", {}, 1, {E}}

rcollyer

2:00 AM

What does the French mean?

CHM

The Treachery of Images

The Treachery of Images (La trahison des images, 1928–29, sometimes translated as The Treason of Images) is a painting by the Belgian René Magritte, painted when Magritte was 30 years old. The picture shows a pipe. Below it, Magritte painted, "Ceci n'est pas une pipe" (), French for "This is not a pipe." The painting is not a pipe, but rather an image of a pipe, which was Magritte's point: The famous pipe. How people reproached me for it! And yet, could you stuff my pipe? No, it's just a representation, is it not? So if I had written on my picture "This is a pipe," I'd have been ly...

It means "this is not a pipe"

rcollyer

I can parse a very little of it due to some Spanish in high school, a smidgen of Latin, plus an extravagant amount of word play in English. :P

@CHM The switch to that form has unintended consequences:

In[59]:= Clear[test]
test[a : ((b__ | c : {__}) ..) ] := {{b}, {c}}
test[{124}, 4, {5}, 2]

Out[61]= {{4, {5}, 2}, {{124}}}

CHM

Hmm. I'm not well-enough versed in MMA to even guess why this is so.

Try this: test[a : ((b : {} | c) ..)] := {{b}, {c}};

rcollyer

@CHM b__ is greedy, so it grabs as much as it can in a row.

In[74]:= Clear[test]
test[a : ((b : {} | c) ..)] := {{b}, {c}};
test[{124}, 4, {5}, 2]

Out[76]= test[{124}, 4, {5}, 2]

CHM

@rcollyer why are you testing with this?

rcollyer

2:12 AM

I'm trying to fix/bullet proof the code I wrote for this.

CHM

ok

rcollyer

the part I'm trying to get running is where I can compare auxillary data (i.e. the data passed into DataListPlot is a tuple like in ErrorListPlot) across data sets, and use that info to change how each point is plotted.

CHM

2:31 AM

ok

good luck.

I'm answering a couple of questions in the Biology Beta. Poor them.

88% answered.

rcollyer

@CHM eww. And w.

(The pun only works if it is set up correctly.)

Theoretical Physics is worse: 83%, arguably a harder field, though.

CHM

haha

Hmm. I'd say it's just a matter of finding a healthy number of knowledgeable contributors

rcollyer

remember what I said about extravagant amounts of word play? yeah, I use it for puns.

CHM

There's bound to be more biologists than theoretical physicists, probably because it's "harder" yeah

rcollyer

The difficulty they're having over on th-phys is attracting a number of different specialties, in addition to having people feel comfortable enough to post.

CHM

2:42 AM

theoreticalphysics.stackexchange.com/questions?sort=unanswered

Gives me the creeps.

I love physical chemistry, not sure I'd have what it takes to do pure physics.

rcollyer

me, too. And, my user_id over there is 6.

CHM

Lol.

I'm having a hard time to interpret mass spectra

Forget me learning about black hole radiation.

rcollyer

Never tried, myself.

@CHM ditto. although, it is an interesting topic as long as you don't have to touch the math. I'm a theoretical physicist and GR makes my brain hurt.

CHM

Haha.

rcollyer

BTW, Mr.W just crossed the 12k mark.

CHM

2:48 AM

I've had a brief encounter with GR, not much math though. I never even worked with tensors (yet).

I saw. That's a lot.

rcollyer

Our own Jon Skeet.

@CHM you've worked with some of the ideas needed in GR, but few make the connection.

CHM

Jon Skeet... how does he manage?

@rcollyer well, I've bought this book, read the introduction. I'm keeping it for a more mature me.

rcollyer

@CHM A dot product is $a^i b_i$, but $a^i$ is the dual of $a_i$, and in Cartesian space this has the same entries as $a^i$. But, this isn't always the case, like in QM where the dual is the complex conjugate. For non-Cartesian spaces, the difference becomes more dramatic.

Also, $a_i b_i$ defines a 2$^\text{nd}$ rank tensor (matrix) in "real" space while $a^i b^i$ does the same thing in the dual space.

CHM

Hmm.

rcollyer

Although, $a^i b_j$ is actually a matrix like we'd think of it. The other two are just weird, IMHO.

CHM

2:55 AM

I'd have to read a wiki on the notation.

Interesting, though.

rcollyer

@CHM He answered 13 questions today. Compare that to my 44 in the 76 days we've been in beta. He's a machine, probably from the future. Or, a collective organism like Mr.W.

CHM

Haha

rcollyer

@CHM that may do more harm than good.

Hi @Searke

CHM

@rcollyer you mean reading the wiki?

rcollyer

@CHM yeah, their math stuff can be nightmarish to decipher.

CHM

3:02 AM

I agree

still sifting through the unanswered Qs on Biology.. some questions must be asked by braindeads.

Or posessing extreme intellectuall laziness.

rcollyer

wouldn't be surprised. I wonder if they have a good mod team there.

I mean, FFS....

Night.

bye

4:56 AM

@rcollyer C# got 3k questions the past week! That's 3 times more than what we've gotten in 70 days. So you're doing pretty fine there :)

Verbeia

5:45 AM

@RM agreed, and more newbie, easy-to-dash-off-an-answer questions

acl

11:12 AM

@rcollyer I think the reason theophys has so many unanaswered questions is that the scope is way too broad; some question are nice but would require one to sit down for a few hours to do a calculation to answer; others are more philosophy; and so on.

F'x

@acl I agree with you on this one; there are not many questions there that I can say I fully understand, a few for which I could provide a high-quality answer

so, unless the userbase is large enough to have at least two or three frequent users in each specialized field, it will not really work

currently, it's mostly “Q field theory and relativity”.SE

acl

@Fx yes, not uncommon

rcollyer

2:50 PM

@acl absolutely, even the answerable questions are tough.

@Verbeia although, I definitely have some of those types of answers here too. :) But, that was a problem I've encountered before.

@RM I didn't say I was doing badly. Just that Jon Skeet was far outstripping what I've been producing.

rcollyer

5:11 PM

@EliLansey and @RM I've sent you both updates to DataListPlot. Tell me if it breaks.

rcollyer

5:35 PM

It appears that we have two questions (1, 2) at the top of the Hot List at the moment.

Heike

@rcollyer And we're on the main page of stackexchange again. That probably means that something bad is about to happen.

rcollyer

5:51 PM

@Heike We've got the top 2 hot questions, so I'm not surprised we're on the front page. But, yeah something bad is probably going to happen ... watch it will rain poor questions down on our heads. :)

R.M

@rcollyer thanks, it looks pretty good. I'm still trying to understand some of the details (which I believe is domain specific). Am I right in understanding that PlotMarkerFunction is the crux to plotting it the way you want it?

It doesn't have a "default" behavior — what should I expect if I input just a matrix to it, without specifying any relationships?

rcollyer

@RM Yes, PlotMarkerFunction is the key. I should have disable PlotMarkers, itself, but didn't.

@RM But, it does, or should. It uses Point[{#1, #2}]& as the function if you don't specify anything. What's showing up?

R.M

Part::partw: Part 1 of {} does not exist. >>
Part::partw: Part 2 of {} does not exist. >>
Part::take: Cannot take positions 3 through -1 in {}. >>
ComparisonFunction::typearg: Comparison function {}[[1]] does not exist. Aborting.

rcollyer

But, it does require a function to be passed in if you want to change the PointSize.

@RM Well, that's helpful ... :P

R.M

I tried DataListPlot[RandomReal[1, {20, 2}]. Looking through the .m file now to see what could cause it

rcollyer

5:59 PM

It's dying inside makeMarkerFunction. stdform[globals] is supposed to put everything in standard form, except without any "Globals" specified, there won't be any.

Also, need to fix that damned message ...

@RM Add the line stdform[{}]:={} just after the other definitions of stdform. It clears up the problem.

R.M

@rcollyer Thanks, that does it. I'll fiddle with it some more today. Gotta get back to work now :)

rcollyer

@RM Have fun. Oh, as far as I know, nothing in there is supposed to be domain specific.

R.M

@rcollyer Oh, I know. I meant the example with the PlotMarkerFunction... I was trying to understand why you were doing what :)

rcollyer

6:14 PM

@RM yes, the example is very domain specific. I'm plotting which one is the ground state, i.e. lowest energy. I just have to put together an example, now, of ErrorListPlot built on top of DataListPlot to complete the demo. :)

Verbeia

7:07 PM

@rcollyer @Heike hot questions drive traffic. We clicked up another notch in visits/day.

rcollyer

@Verbeia I understand it drives traffic. I just enjoyed the bit a fear mongering suggested by Heike, though.

Eli Lansey

@rcollyer will do

F'x

I feel like I have won the SE SuperCollider lottery with this "edit matrix in table form" question

rcollyer

@Fx pretty much. Now I can have my mathematica and spreadsheet, too!

F'x

@rcollyer but I have earner 25 rep from it, I was almost rep-capped when I answered :)

rcollyer

7:21 PM

@EliLansey Note, the small bug fix posted above.

Eli Lansey

@rcollyer I saw that.

F'x

there was a time when you could use that sort of opportunity to give a bounty… those were the days

rcollyer

@Fx well, that's no fun.

@EliLansey I've made a few minor changes today, also, and may send another update tomorrow.

F'x

@rcollyer I'm not that addicted… mostly because I reached 2k today anyway, which means I stopped being annoyed by seeing the site as low-rep user

Eli Lansey

@rcollyer ok. it's a really nice piece of code. something like that should be included by default in ListPlot

rcollyer

7:24 PM

@Fx That should teach you a lesson: don't answer questions when you're that close to rep capping. :P

@Fx I hear you on that point.

Eli Lansey

@Fx Congrats! One of these years I'll make it...

rcollyer

@EliLansey Thanks. It's not as bulletproof as it needs to be, yet, but it is getting there. My plan is to re-implement ErrorListPlot on top of it just to show that it can be done. :)

F'x

@rcollyer well, that would have meant doing some real work… thus I stayed and answered :)

rcollyer

@Fx okay, as long as your priorities are correct. :)

F'x

actually, I felt so unproductive at work today I left early and spent the end of the afternoon donating blood just to feel like I could contribute to something!

2

rcollyer

7:26 PM

Lol

I should go. Talk to you all later.

Heike

@Verbeia But our questions/day is dropping again :-(

F'x

see you

@Heike don't obsess on stats; the community feels dynamic, I don't see why it shouldn't grow

Heike

On the bright side, we only need 4 more users with 200+ rep to reach the avid users quota

F'x

better a cool, organic growth than a sudden rush to graduation

Heike

@Fx Obsessing about numbers if what I'm trained for.

3

@Fx I'm not advocating a quick graduation.

rcollyer

7:32 PM

@Heike I agree. I don't think we quite have the depth of users needed. We're going to get there, and relatively quickly compared to other sites. But, we're not there, yet.

Just my 2 cents. I need to go meet my ride. Bye.

Reb.Cabin

11:48 PM

In case Leonid shows up here, I have a gist for him gist.github.com/2296390

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