Wolfram Mathematica

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2:09 AM

@belisariushassettled Where does it say it was a Matlab question?

Oh right, in the comments to your answer

I confess I upvoted it because I thought it was an interesting image processing question, a bit like the "find something on Mars" question that went viral.

J. M.

2:24 AM

@Verbeia, it was all good, yes, up until he said that comment. Not unlike saying something inappropriate in the middle of an otherwise splendid date.

belisarius has settled

@J.M. Splendid dates are sometimes inappropriate per se

J. M.

@bel, haven't bumped into that, tho. :)

belisarius has settled

2:39 AM

@J.M. Me neither. T'was my grandpa who told me

11 hours later…

Oleksandr R.

1:24 PM

Q: Mathematic-Related Problem?

I learn in university, and we have a task. We have a semester to work on a project related to mathematics in Wolfram Mathematica. We need to tell, what we are planning to do, and I simply have no idea. (I learn it only since 4 months, and I am not that expert at it.) What would you suggest me? Pr...

education

We have a lot of "do my work for me" questions, but this seems to be the first "have an idea for me" type of question

@belisariushassettled I've often wondered how such people function in life. Maybe they don't

blochwave

1:39 PM

@OleksandrR. Maybe there will be a follow-up question: "Thanks for the idea, how do I solve it?"

Jacob Akkerboom

2:09 PM

Did anybody else find that the link in the INTERNAL SELF-TEST ERROR message to "find out if this problem is known, and to help improve the Wolfram System by reporting it to Wolfram Research" does not work? Reporting it is on my to do list

1 hour later…

J. M.

3:23 PM

@OleksandrR. Unfortunately, muddling through life decisions is more commonly done than you think. You'd prolly be stunned at how much is decided upon by common folk through impulse or happenstance.

1 hour later…

hYPotenuser

4:30 PM

I've got a list of associations that I want to regularize or reshape. Some of them look like <| a->1, b->2, d->4 |> and some of them look like <| a->1, c->3 |>. I want them to look like <| a->1, b->2, c->Missing[], d->4 |> and <| a->1, b->Missing[], c->3, d->Missing[] |>, i.e. they all have the same number of keys. Not knowing much about structured data, I don't know what to call this operation or what to look for in the docs

Is there a built-in for this, or should I just map something with KeyExistsQ over them all?

Michael Hale

@hYPotenuser KeyUnion

KeyUnion@{<|a -> 1, b -> 2, d -> 4|>, <|a -> 1, c -> 3|>}

hYPotenuser

Beautiful, @MichaelHale! thanks so much.

That's a reasonable name for the operator, too. A union of the keys.

1 hour later…

Mauris

5:45 PM

Any quick and easy way to color part of a 3D plot?

I'd like the x > 0 half to be, say, blue.

J. M.

6:10 PM

@Mauris

Plot3D[f[x, y], {x, -3, 3}, {y, -3, 3}, ColorFunction -> Function[{x, y, z}, If[x > 0, Blue, Red]], ColorFunctionScaling -> False]

2 hours later…

Mauris

7:44 PM

@J.M. Cool, thanks!

After posting, my first thought was to create two Plot3Ds that plot the two halves of the function, and combine them with Show[], but I don't know how to do that, either.

Mauris

7:57 PM

Maybe I could just do Plot3D[{Restrict[f[x, y], x < 0], Restrict[f[x, y], x > 0]}, ...]

(Except with some function that actually exists...)

@J.M. (This solution works, but it looks a bit ugly on the x=0 line. Also, I like the shading the defaults give you.)

Patrick Stevens

8:11 PM

Wow, never knew evaluate-in-place was a thing (mathematica.stackexchange.com/questions/99877/…)

the more you know!

magic

Patrick Stevens

8:42 PM

I think there's a question somewhere about how to create the nice little summary-boxes like the display form of SparseArray or Dispatch, but I can't find it - does anyone know where it is?

Sjoerd C. de Vries

8:55 PM

@PatrickStevens you can find the trick in my BVH motion capture answer

A: How to build a bvh (a motion capture file format) player in Mathematica?

TL;DR: A package (Mathematica v10) can be found at the very bottom of this post. UPDATES 6: Tiny update: Import can now use the ".bvh" extension to determine the import type. The code that does this is ugly, but I don't see any other way at the moment. out = Import["C:\\Female1_C03_Run.b...