Re: Inverse Matrix Function appears a bit wonky

[Geraint Paul Bevan]

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Robert A. Macy wrote:
| I tried a simple test of the inverse function using a "made
| up" matrix...
|
| testmatrix =
|  1 2 3 4
|  2 2 3 3
|  1 2 1 2
|  3 2 2 1
|

You have chosen a singular matrix (i.e. its determinant is zero) and it
does not therefore have an inverse.  Note the warning below:

octave> m = [1 2 3 4; 2 2 3 3; 1 2 1 2; 3 2 2 1];
octave> det (m)
ans = 0
octave> inv (m)
warning: inverse: matrix singular to machine precision, rcond = 0
ans =

~  3.00000  2.00000  2.00000  1.00000
~  0.33333  1.33333  0.33333  1.66667
~  0.33333  1.00000  2.00000  2.00000
~  0.66667  0.50000  0.75000  0.00000

octave>

- --
Geraint Bevan
http://homepage.ntlworld.com/geraint.bevan

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