871 reputation
614
bio website
location Universidade de São Paulo, Brazil
age 29
visits member for 2 years, 7 months
seen Mar 24 at 18:13

I am currently a post-doc at the Physics department at the University of Sao Paulo. My interests are in Statistical Physics, stochastic processes and magnetism. More importantly, I really value simple and solid explanations to important problems in any science.


Jan
15
comment More efficient matrix-vector product
@rcollyer What exactly do you mean by generating in eigenspace: if $A = S \Lambda S^{-1}$ then I should do $Ax = S \Lambda S^{-1} x$? Also, I read your link on spherical components, but didn't really get how that would translate to the present problem. Again, thanks for the help.
Jan
15
comment More efficient matrix-vector product
Hi all. Sorry for the delay in answering. Yes, $A$ will usually have full rank. It is also symmetric and has zero diagonal. But I don't know all the $x$'s in advance, so I need one dot product at a time. Thank you all for the support.
Jan
15
asked More efficient matrix-vector product
Jan
8
awarded  Popular Question
Dec
8
comment Converting other C++ classes to MTensor in LibraryLink
@halirutan Oh yeah! Very much :)
Sep
12
awarded  Caucus
Aug
25
accepted Computing polynomial eigenvalues in Mathematica
Aug
25
comment Computing polynomial eigenvalues in Mathematica
@J.M. Amazing answer. Thank you a lot.
Aug
24
awarded  Nice Question
Aug
24
comment Computing polynomial eigenvalues in Mathematica
@ruebenko the example above comes from solving Newtons law for a system of particles. Gotta think about more examples. :)
Aug
24
asked Computing polynomial eigenvalues in Mathematica
Aug
23
comment Odd behavior of GridGraph and DirectedEdges
@DavidCarraher Thanks for the answer. I'll report it as a possible bug. I am not sure this is related, but GridGraph draws the graph differently from other graphs.
Aug
23
asked Odd behavior of GridGraph and DirectedEdges
Aug
16
accepted Mathematica + Numerical Recipes
Aug
16
accepted Circuit drawing in Mathematica
Aug
14
comment LeastSquare Solution for the Continuous Time Lyapunov Equation
No. I saw that on the documentation for LyapunovSolve but I don't understand the Mathematics of e Kronecker product.
Aug
14
comment LeastSquare Solution for the Continuous Time Lyapunov Equation
For least squares what I do is write a symbolic symmetric matrix in the sorts of R = Array[r,{n,n}]/.r[i_,j_]/;j<i->r[j,i]. Then I do {b,B} = CoefficientArrays[Flatten[A.R + R.A[Transpose] + G], vars] where vars = DeleteDuplicates@Flatten@R. Finally, I do LeastSquares[B,b].
Aug
13
asked LeastSquare Solution for the Continuous Time Lyapunov Equation
Aug
1
comment Converting other C++ classes to MTensor in LibraryLink
@LeonidShifrin I'm sorry Mr. Shifrin. I am still learning about LibraryLink and most of what you said I did not understand. Say I have a 2x2 matrix a[i][j]. Then what I want is to define a 2x2 MTensor m such that m[i][j]=a[i][j]. Hopefully, it would be nice to do this without a double for loop with m[i][j]=a[i][j].
Jul
31
comment Converting other C++ classes to MTensor in LibraryLink
@LeonidShifrin I have edited the question with a situation where it is possible to access the data via a pointer. In that case, a simple solution exists?