Re: Testing for invertible matrix
- To: mathgroup at smc.vnet.net
- Subject: [mg39716] Re: Testing for invertible matrix
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Mon, 3 Mar 2003 23:48:47 -0500 (EST)
- Organization: Universitaet Leipzig
- References: <b3pgti$7jd$1@smc.vnet.net>
- Reply-to: kuska at informatik.uni-leipzig.de
- Sender: owner-wri-mathgroup at wolfram.com
Hi, looking in a *mathematics book* than into "The Mathematica Book" is a better idea, or is Det[A]=!=0 not a fine test for a matrix A to be invertible ? Regards Jens Bob Harris wrote: > > Howdy, > > If there some means to test whether a square matrix is invertible, rather > than trying Invert[] and having it fail? > > I'm working on a notebook that's searching through randomly generated > matrices, looking for one for which the inverse has certain properties. > Thus inside my search function I have a loop something like this: > > While [... some condition , > t = ... create a matrix ; > q = Inverse[t] ; > > ... perform some computation using the entries in q > to determine if the exit condition will be met > ]; > > But if t is singular, computing the inverse fails. Nevertheless my loop > keeps running for a while, but generates a few more annoying messages > (because access to q fails) before it finally quits. > > What I would rather do is something like this: > > While [... some condition , > t = ... create a matrix ; > If [ t is singular, Continue[]]; > > q = ... inverse of matrix ; > > ... perform some computation using the entries in q > to determine if the exit condition will be met > ]; > > But looking through the mathematica book, I haven't come across a way to do > that. I also considered that Inverse[] would have some means for me to tell > it how to handle the failure condition, but I don't see anything in the book > about that. > > Thanks in advance for any help, > Bob H > Lawrenceville, GA