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May
1
awarded  Electorate
Apr
29
comment appending element to sub list
@MichaelE2: Thank you.
Apr
29
answered appending element to sub list
Apr
26
comment Turning Off Error messages locally
It won't work on subexpressions, though: a=3;myfunction2[x_] = a + Unevaluated@Quiet[1/x] will evaluate a on assignment, but will not evaluate 1/x on calling the function, but instead give (when calling with argument 0) the result 3+Unevaluated[Quiet[1/0]]
Apr
25
comment Kronecker delta notation
You might want to use ^:= so that the rule gets attached to \[Delta] instead of Subscript
Apr
22
awarded  Nice Question
Apr
21
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
reviewed Approve suggested edit on example tag wiki excerpt
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
revised predator prey model with prey refuge
Improved math formatting