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Oct
30
comment How do I display the parameter value in animate, similar to how it's done in manipulate?
@Joe I'm guessing you're using Mathematica version 8, or at least not the newest version. In version 8, I can confirm that Appearance -> "Labeled" doesn't work. Since you accepted the solution, does that mean you're not looking for a workaround anymore?
Oct
29
comment Phase portrait on a cylinder
(+1) I think it looks better with the cylinder added, though...
Oct
28
comment Oval or Bunimovich stadium
Yes, using a case distinction. But as I said initially, you have to make your question more specific so that anyone who answers won't get dragged into an extended discussion trying to hit a moving target because the goal is initially set too broadly. E.g., is speed a main concern, or code readability, or user-friendliness, or extensibility to non-convex shapes, etc. Seems to me like a tutorial would be needed, too.
Oct
28
comment Oval or Bunimovich stadium
Closely related: Poincaré map for dynamic billiard. Both are essentially requests for code, building on a copy of the same demonstration authored by Dan Reznik.
Oct
28
comment Oval or Bunimovich stadium
Of course I know how to do all this because I've worked on it extensively, but I don't think an answer is within the scope of this Q&A format. You would have to narrow down your question to a specific Mathematica issue. I would prefer to post my own code instead of trying to modify the code you posted without any comments.
Oct
28
comment How to redefine the type of multiplication in Det
The Block approach doesn't work for numerical matrices, e.g., Block[{Times = f}, Det[PauliMatrix[2]]]
Oct
28
comment How to redefine the type of multiplication in Det
Probably it would be good to explain what your ultimate goal is, and what the specific properties of the function Fun are. Without that information, there is a good chance that any effort to answer this could be misdirected.
Oct
28
comment Derivatives of functions with arbitrary number of variables?
@rhermans Can you explain what you think the OP means? I do not understand it. This may be because the question is too broad and "formalism" is not defined.
Oct
27
comment A Product function for matrix products
Sometimes defining a new function for a simple task can make the code less readable. In this instance, I think that is the case because the syntax as shown by @DanielLichtblau is concise and sufficiently expressive to be self-explanatory.
Oct
26
comment Derivatives of functions with arbitrary number of variables?
When you try D[f[x1, x2, xn], x2] you do get an unambiguous result, right? So I think you have to state the problem more clearly with an example.
Oct
26
comment Poets of the 19th century
@DumpsterDoofus I thought that was Mao Zedong...
Oct
25
comment Poets of the 19th century
Lenin was a poet??
Oct
25
comment Why is it so complicated to simplify a complex conjugate?
@BobHanlon is right. All the issues here are caused by some very basic misunderstandings about syntax. Assuming only affects commands that take the option Assumptions. Simplify is one of those, but it must be inside the Assumptions. The other code block contains logical statements which have no effect at all on the subsequent lines because they aren't put into the form of Assuming or $Assumptions. I think there must be a duplicate but can't find it right now.
Oct
25
comment Why is it so complicated to simplify a complex conjugate?
Related: Remove annoying Conjugate
Oct
23
comment Pull out scalars from NonCommutativeMultiply in commutator of SU2 spin algebra
@DanielLichtblau Just for completeness: There's also this related question where your linked FAQ is equally relevant (of course it's relevant for lots of other questions...)
Oct
22
comment Pull out scalars from NonCommutativeMultiply in commutator of SU2 spin algebra
I would do this without NonCommutativeMultiply altogether. But if you do want to go that route, I think you will have to provide the code that you tried for your commutator algebra. Otherwise we'd have to re-invent the wheel before answering.
Oct
21
comment Why doesn't FullSimplify simplify expressions with DiracDelta?
@NikkiBisschop I edited my answer to include more examples, and what I say in the first paragraph of the edit is based on your comment. It is in fact the answer to your overarching question why DiracDelta isn't simplified as such. One needs the information identifying the integration variable to make the correct simplification.
Oct
21
comment Why doesn't FullSimplify simplify expressions with DiracDelta?
@Dr.WolfgangHintze I just checked in version 8.0.4, and I cannot reproduce your problem. It simplifies correctly on my system, even in the older version. This is on Mac OS 10.7.5.
Oct
21
comment Why doesn't FullSimplify simplify expressions with DiracDelta?
@Dr.WolfgangHintze Ah, so this time it was good that I used version 10.0.1. There, it does simplify exactly to what you quoted...thanks for pointing out the issue with 8!
Oct
21
comment Why doesn't FullSimplify simplify expressions with DiracDelta?
@Dr.WolfgangHintze I did find a shortcoming when I switched the variables in your example and replaced the square by a symbolic n - see my edit. But I think one gets pretty decent results all in all.