9,945 reputation
2072
bio website
location
age 42
visits member for 2 years, 3 months
seen 7 hours ago

2d
comment How can I represent this automorphism of Q(i,a)?
What is $\mathbb Q(i,a)$?
Apr
17
comment How to get mathematica to simplify a result
@Mr.Wizard: Do you possibly have packages autoloaded which might affect this?
Apr
17
comment How to get mathematica to simplify a result
Just tried, and for me version 7 doesn't do it either, so it doesn't seem a version problem.
Apr
17
comment How to get mathematica to simplify a result
Version 8.0.0 doesn't simplify that expression either.
Apr
17
comment How to get more accurate orthonormal eigenvectors?
Also note that a higher precision at the source may mean significant higher calculation time, since the processor floating point capabilities cannot be used any more.
Apr
17
comment expression contained across multiple cells
One option would be to factor out some of the code into separate definitions. If your code is so long that you would like to collapse parts of it, then doing so is probably a good idea anyway.
Apr
15
comment expression contained across multiple cells
I don't think so. But given that you can format the expression inside the cell using the enter key, what would be the use of multiple cells?
Apr
14
comment combining plots
And what is the question?
Apr
14
comment combining plots
@Pickett: Yeah, when I started writing the answer, that part was not yet there in the question ;-)
Apr
14
comment combining plots
Did you store the plot in myplot?
Apr
13
comment Sum does not converge, but I think it should
Sum[Boole[!x \[Element] Integers],{x,1,Infinity}] also is reported to not converge, despite not using the problematic IntegerQ function.
Apr
13
comment Solving huge equations
If this takes too long, maybe you should consider whether you really need the analytic solution. Depending on what you do, it may be sufficient to find solutions for given numeric values of $f$ and $c$ (in which case you can wait with Solve until you have inserted those values, thus giving a much simpler expression to solve). You might even not need the complete set of solutions, in which case you may consider using FindInstance after inserting values.
Apr
13
comment Conjugating symbolic expression
An example where it doesn't work: Sqrt[-x^2]. ComplexExpand[Conjugate[Sqrt[-x^2]]] gives -I Sqrt[x^2], but ComplexExpand[AltConjugate[Sqrt[-x^2]]]` gives I Sqrt[x^2]
Apr
12
comment Why does Mathematica list the variables in a double integral backwards?
Well, you just have to use the physicists' convention to get the right ordering of the variables: $\int_0^a\mathrm dx \int_0^{f(x)}\mathrm dy\,(x+y)$
Apr
12
comment predator prey model with prey refuge
I think NDSolve is the function you are looking for.
Apr
12
comment Mathematica does not respect tensor order?
I don't have experience with SymmetrizedArray (it's a Mathematica 9 feature, and I only have access to Mathematica 8), so I cannot tell you whether that would be the correct or best approach. The problem here is that Mathematica treats all unbound variables as scalars during evaluation, and there's AFAIK no way to override that behaviour for specific variables.
Apr
12
comment Equivalence under common permutations
Wow. Just wow. Thank you!
Apr
11
comment Solving a single equation with multiple parameters
One other way (which is still better than numeric fitting) could be to insert several exact values for x and solve for the resulting equation system.
Apr
11
comment Solving a single equation with multiple parameters
Another option does involve SolveAlways (but on your equation it doesn't seem to do anything useful either, but then, I don't have access to the latest version of Mathematica, so maybe it improved).
Apr
11
comment Solving a single equation with multiple parameters
BTW (unrelated, but important): You should avoid uppercase single letter names because they are often builtins which may cause you trouble. In your case you're lucky because while both C and D have existing definitions, they both involve function call syntax. But as soon as you add E to the mix, you'll get into big trouble because that's Euler's number. As a general rule, it is a good idea to start all your own names with lowercase letters, because Mathematica's predefined names never do.