1,511 reputation
513
bio website math.upatras.gr/~spawn
location Brazil
age 37
visits member for 2 years, 9 months
seen Oct 2 at 22:21

Mathematics, PDEs, General Relativity and symbolic programming with Mathematica.


May
22
comment Underflow occurred in compilation
You can set a value as the infinity and for everything greater you set the Exp to zero. I assume that you are studying something about Julia sets so the divergence area is not the one that you are mainly interested at.
May
22
comment What kind of hypergeometric function is it?
What version of Mathematica you have?
May
21
comment Performance of Dispatch and lists of Rules
@JacobAkkerboom so in fact you want a mechanism to check the "sanity" of your dispatch tables.
May
21
comment Performance of Dispatch and lists of Rules
@LeonidShifrin he can try to implement something using $Pre or some other mechanism, the idea is to detect when an Update is called and update the dispatch tables if necessary.
May
21
comment Performance of Dispatch and lists of Rules
Observe that if you call the dispatch table after the Update and before the substitution the substitution is not slowed down. So perhaps you need to "overload" Update in a such fashion that will also update the rules if a symbol contained in one is updated.
May
21
comment Question regarding function definition overloading / argument passing test
you can also use /; (Condition).
May
20
comment Counting a cardinality of a subset satisfying special property
You can use Select and Length to do it.
May
18
comment Cannot solve system of linear equation sums?
Is the variable x a list of values? If yes then you should use x[[k]] instead of using a subscript.
May
17
comment Tricky selection of elements based on their position
@Rojo with {-1} will access the base elements no matter what the structure is and this in combination with a generic constraint on the indexes can make it more general.
May
17
comment Tricky selection of elements based on their position
Well you can try just Reap[MapIndexed[Sow[#1,#2[[1]]>=#2[[2]]&&#2[[3]]>=#2[[4]]]&, b, {-1}], True] but I don't think will be much faster though.
May
16
comment Tricky selection of elements based on their position
You can try MapIndexed for level {-1} in combination with Reap/Sow.
May
16
comment Can you form a list with elements which are terms from an equation?
You can expand your equation and then apply List.
May
14
comment Substitution to write out powers of expressions
Have you tried Eliminate?
May
14
comment How to deal with zero in NDSolve in mathematica?
Probably the initial condition is a limiting initial condition, this is common when the general solution is expressed by transcendental and special functions. Perhaps you should perturb t by $\epsilon$ and then take $\epsilon\rightarrow 0$.
May
14
comment How to deal with zero in NDSolve in mathematica?
are you sure this is a sound set of initial conditions?
May
13
comment Integrate of Heaviside Function returns an error answer
Define k first.
May
10
comment Find the position of a string element, knowing only part of the string
You need string patterns and Friends, e.g. StringFreeQ, StringPosition, ..
May
10
comment Optimizing a simple calculus using a list of matrices - Repeated dot product between a vector and a list of matrices
Use /@ like {q1,q2}.#.{q1,q2}&/@A.
May
9
comment Numerically solve 2nd order differential equation with singularity
I will just quote "A powerful way of computing the twelve Jacobian elliptic functions for real or complex values of both the argument z and the modulus k is to use the definitions in terms of theta functions given in ..." as found in NIST Handbook of Mathematical Functions pg. 566
May
9
comment Numerically solve 2nd order differential equation with singularity
Btw have you tried expressing your potential using theta functions?