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Jul
1
comment Answer when integrating by partial fractions
Related question
Jun
30
comment Saving graphics in Adobe Illustrator .ai format
If you look at the header of an AI file, it's actually just a PDF file with some additions. That's why it can for example be viewed in Preview on OS X without having to install Illustrator. AI format used to be based on EPS, but that's no longer the case.
Jun
30
comment Speed up series expansion
To get a consistent expansion, you probably want to do something like this instead of the approach in your question: Normal[Series[1/(1 + x)^2 y z /. {x -> ϵ (x1 + x2 + x3 + x4), y -> ϵ (y1 + y2 + y3 + y4), z -> ϵ (z1 + z2 + z3 + z4)}, {ϵ, 0, 2}]] /. ϵ -> 1. In that case, this is probably a duplicate of Multivariable Taylor expansion does not work as expected
Jun
30
comment Problem When Trying to Export Graphics with Transparency to SVG
For the Firefox problem, I added a link to my answer that fixes this issue.
Jun
30
comment Problem When Trying to Export Graphics with Transparency to SVG
I agree about Firefox, but it can be easily fixed with <img src="bad.svg" style="width:360px;height:360px;". It's unrelated to the background issue, see here. So basically, one should call this a bug that has apparently been fixed in version 9.0.1 but not in 9.0.0.
Jun
30
comment Efficient way to build a certain quadratic matrix
How come the question got fewer upvotes than it received answers? It should have at least that number (plus one).
Jun
29
comment Why does Evaluate fail?
(+1) This question seems to have been re-posted later... I overlooked this, otherwise I would have referred him to your answer.
Jun
29
comment How to speed up minimization of function
On my computer, the following is faster in the Plot command: PlotPoints -> 8, MaxRecursion -> 2
Jun
29
comment How to speed up minimization of function
I think my code is slower than your (without Evaluate) because I replaced PlotPoints by MaxRecursion. But I can't think of a way to make it faster (even though you could add Evaluate to my solution, the speed doesn't change). I thought you wanted to get rid of the error messages, and using ?NumericQ is the most speed-friendly way I know that does this.
Jun
28
comment How to create a writable and clearable symbol?
@Ruslan ToExpression is just a more high-level function that can act on expressions (even lists of expressions). The strings accepted by Symbol are limited to be valid symbol names. Because of this relationship, you can definitely use ToExpression in place of Symbol when you're sure you've constructed a valid symbol name string.
Jun
28
comment Output of mathematica. Quaternion to Matrix
@danciulian It looks like you should first familiarize yourself with the basics of the language Mathematica. The questions you're asking smell like homework problems, and of course the purpose of such problems is to get you to think about the solution yourself. First look through the documentation for all the keywords in the code you pasted in your question.
Jun
28
comment How can I compute a functional derivative of a composed function?
How did you come to the conclusion that what you call the "correct answer" is actually correct? I think it's just plain wrong.
Jun
26
comment Which functions automatically generate new functions?
To amplify @OleksandrR.'s point: isn't Function a function which creates a function? Then there are also things like ColorData, and in fact these kind of functions with string arguments seem to have proliferated lately. Maybe you're only interested in NumericFunctions?
Jun
26
comment A derivative encountered in matrix factorization using gradient descent
The result you cite is not wrong, it's just not in the form you want. What is the practical use case where this result doesn't agree with what you want to achieve? In particular, why do you need infinity as the upper limit if your goal is an actual matrix factorization (since matrices have a finite rank)? I'm asking mainly to understand if this is worth the trouble...
Jun
26
comment Is there a way to increase the smoothness of a cylinder?
@BurkardPolster I added a different approach to my answer that creates the cylinders in such a way as to preserve them during Export.
Jun
26
comment Is there a way to increase the smoothness of a cylinder?
That does the trick! With Method -> {"CylinderPoints" -> {600, 1}} your plot seems to be just as responsive as the Tube version. So the speed isn't an issue anymore, and I'll edit my answer to account for your update.
Jun
25
comment Symbolic evaluation of the sum of KroneckerDelta
@george2079 yes - that works fine. It's the infinite case that causes trouble.
Jun
25
comment Symbolic evaluation of the sum of KroneckerDelta
In my opinion this should be tagged as a bug because it's a regression. In version 9, the sum works with any finite numerical upper limit, but not with Infinity. But in version 8, the simplification works even when the upper limit is Infinity.
Jun
25
comment Symbolic evaluation of the sum of KroneckerDelta
@entron You're right, it works in version 8 and not in version 9! I'll think about it. Seems like a bug to me.
Jun
25
comment Collect terms in a sum
@george2079 Well, that's what the question is about.