[SciPy-user] Inverse of complex matrix
David Cournapeau
david@ar.media.kyoto-u.ac...
Sat Nov 10 02:11:05 CST 2007
Roger Herikstad wrote:
> Dear scipy users,
> I am trying to invert a 12 by 12 complex matrix R using
> scipy.linalg.inv(), but the round-off errors seem a bit too big. If I
> do scipy.dot(Ri,R), the first row of the resulting matrix looks like
> this:
>
> array([ 0.953125 +0.j , 0.06542969+0.01171875j,
> 0.08154297+0.15234375j, -0.078125 -0.09375j ,
> 0.19140625-0.0859375j , 0.08203125+0.140625j ,
> -0.08398438+0.0078125j , -0.02539062-0.03125j ,
> -0.06738281+0.015625j , -0.04736328+0.15820312j,
> -0.09057617+0.02832031j, 0.109375 -0.0625j ])
>
>
> Is this normal? Inverting a 2x2 matrix produces the expected result.
> I've attached a pickle of my matrix. Thanks!
As a rule, you should not invert a matrix unless you *really* need it.
For example, if you want X in
A X = B, with A a matrix, B and X vectors, inverting A should be
avoided. Some other methods are better suited (numerically speaking),
depending on A and what you are trying to do.
The mathworks have good introduction on this topic, if you look for
online help on inv, pinv and so on:
http://www.mathworks.com/access/helpdesk/help/techdoc/ref/inv.html
cheers,
David
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