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RMS error of matrices

Hi,
I have 2 large matrixes (2048x2048), and have taken one away from the other to get a 'difference' matrix. I want to quantify this matrix by using an RMS error, however if I use a standard RMS error formula I get another 2048x2048 matrix.
Is there a way to get a single representative RMS value out?
Thanks,
Richard

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2 Answers

Answer by Walter Roberson
on 6 Apr 2011
 Accepted Answer

Isn't it usually
sqrt(mean(A(:).^2 - B(:).^2))

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Answer by darksideofthemoon101 on 6 Apr 2011

I've been using
rms = sqrt((A - B)^2))
How dissimilar are these equations?

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When A and B are arrays then A-B is an array, and (A-B)^2 is
(A-B)*(A-B) which is a matrix multiplication which will produce an output the same size as A (in this case.) sqrt() of that would then be the same size.
Nothing in your code calculates the _mean_ portion of "RMS". Root MEAN square.
Possibly I should have suggested
sqrt(mean((A(:)-B(:)).^2))
but I am too tired to look up the definition at the moment.

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