Solving linear equations with symbolic RHS
- To: mathgroup at smc.vnet.net
- Subject: [mg30141] Solving linear equations with symbolic RHS
- From: "Tony MacKenzie" <mackenzi at usq.edu.au>
- Date: Tue, 31 Jul 2001 04:27:13 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
Once again I would like to thank everyone who helped with my last post. This question is more general and therefore probably much more difficult to answer. I am trying to solve linear equations of the form A.x=b. A is a completely numeric matrix but b is a symbolic vector. I have tried Solve and LUDecomposition but neither of these seem to work very well when b is a symbolic vector. What has worked the best for me is to invert the matrix A (There is no problem with ill-conditioning) and to multiply by the symbolic vector b. However, what slows this process down is when I expand the result. Ainv=Inverse[N[A,16]]; soln=Ainv.N[b,16]; Expand[soln]; (This last steps slows down dramatically as the size of the problem increases). Each element of the symbolic solution vector may have a large number of terms. I realise this question I am posting is quite vague but if anyone has any ideas it would be greatly appreciated. Tony MacKenzie