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Re: Novice question on A \ b
From: |
Geordie McBain |
Subject: |
Re: Novice question on A \ b |
Date: |
Fri, 11 Mar 2005 12:05:41 +1100 |
User-agent: |
Mutt/1.5.6+20040907i |
On Thu, Mar 10, 2005 at 04:41:10PM -0800, John B. Thoo wrote:
> Hi. According to the Octave manual, when using A \ b, if the
> coefficient matrix is singular, Octave will print a warning message and
> compute a minimum norm solution.
>
> This is what I tried.
>
>
> octave:18> A = [ [1, 1, 2, 3]' [0, 0, 4, 4]']; b = [3, 0, -1, 0]'; A \ b
> ans =
>
> 1.40000
> -1.00000
>
>
> I think this is the minimum norm solution, but Octave did not issue a
> warning. What is wrong with my thinking?
I think Octave only warns when a square matrix is (numerically)
singular. Since no nonsquare matrices are nonsingular, it could
reasonably be argued that the warning would be redundant.
Geordie McBain
www.aeromech.usyd.edu.au/~mcbain
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