On Dec 17, 2008, at 8:03 PM, Jason Grout wrote:
> > Tim Lahey wrote: >> >> There are certainly some things you can do with general matrices and >> vectors, but I think doing something like defining A as an nxm matrix >> and allowing various operations on it is a very useful thing. >> Mathematica has some support for this, but I don't think it has a >> general solve. > > > Could you maybe give an example session in Mathematica doing something > like this? > You can define a, and c as vectors and B as a matrix and then do, D[Transpose[a].B.c, c] or D[Transpose[a].B.c, a] If they conform, the operation is valid, and has a simple solution. This comes up in Variational Calculus, particularly in relation to Finite Element Analysis. In FEA, B is actually NN^T where N is the basis vector and a and c are equal and are the vector of nodal displacements/values. I've discussed this once before in a different thread on PDEs. Since Maple didn't support this kind of operation and was my CAS of choice at the time, I wrote a bunch of code to derive element matrices much of which could have been skipped if I could do the above. Cheers, Tim. --- Tim Lahey PhD Candidate, Systems Design Engineering University of Waterloo http://www.linkedin.com/in/timlahey --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to sage-support-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-support URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
