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MathGroup Archive 2003

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Re: Testing for invertible matrix

  • To: mathgroup at smc.vnet.net
  • Subject: [mg39692] Re: [mg39676] Testing for invertible matrix
  • From: Dr Bob <drbob at bigfoot.com>
  • Date: Sat, 1 Mar 2003 22:05:40 -0500 (EST)
  • References: <200303010748.CAA09889@smc.vnet.net>
  • Reply-to: drbob at bigfoot.com
  • Sender: owner-wri-mathgroup at wolfram.com

Det@t==0 is the condition you want.

Bobby

On Sat, 1 Mar 2003 02:48:33 -0500 (EST), Bob Harris 
<NspamITmeLION at MINDnotSPRING.COM> 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
>
>
>
>



-- 
majort at cox-internet.com
Bobby R. Treat



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