Re: Numerical Determinants
- To: mathgroup at smc.vnet.net
- Subject: [mg12955] Re: [mg12922] Numerical Determinants
- From: Daniel Lichtblau <danl>
- Date: Sun, 28 Jun 1998 02:51:46 -0400
- References: <199806240744.DAA03121@smc.vnet.net.>
- Sender: owner-wri-mathgroup at wolfram.com
Rod Pinna wrote: > > Hello all, > > I have a large square matrix, of 30x30 elements (and possibly larger). > Each element is of the form > > Ai,j + Bi,j P > > Where Ai,j and Bi,j are real numbers. Evaluation of this matrix in > symbolic form is very slow. Obviously, numeric evaluation is much > faster. What I want to do is evaluate, with M the matrix above: > > NSolve[Det[M]==0,P] > > Nsolve seems to, as far as I can tell, first evaluate a symbolic > expansion of M, rather than numerically substituting numbers. Is there > a way to get Mathematica to evaluate this in a purely numeric way? > > I've tried Findroot, but the fuction is badly behaved around the roots > of interest, and it doesn't find the roots I'm looking for. Any > suggestions? > > Thanks, > Rod Pinna. > > Rod Pinna > (rpinnaX at XcivilX.uwa.edu.au Remove the X for email) My suggestion is to evaluate Det[M] using interpolation. It is a polynomial in P of degree no larger than 30, so this should be simple. of the work. Daniel Lichtblau Wolfram Research
- References:
- Numerical Determinants
- From: hello@there.com (Rod Pinna)
- Numerical Determinants