# compare the absolute value of each element from two matrices

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Jack_111 on 25 Nov 2014
Commented: Image Analyst on 25 Nov 2014
I have two matrices A and B with the size NxM and I want to compare the absolute value of each element for the two matrices and return the bigger value and then to store the real value in a new matrix.
Many thanks in advance
Image Analyst on 25 Nov 2014
OK. Good. Calling it the "real" value instead of the "max" value was a major oversight initially. But now that you've clarified it, it looks like you now have two correct solutions. Thanks for accepting one of them. You can also vote for both of them too, even though you can accept only one.

Guillaume on 25 Nov 2014
Edited: Guillaume on 25 Nov 2014
Concatenate A and B along the third dimension, get the second output of max along the 3rd dimension of the absolute of that 3d matrix to get the z index. The tricky bit is then using that z value to select A or B. Summing each matrix multiplied by a logical matrix should do it:
a = [1 -2 -3; 4 5 -6]
b = [3 2 1; 8 9 -3]
ab = cat(3, a, b);
[~, idx] = max(abs(ab), [], 3);
c = a.*(idx==1) + b.*(idx==2)

### More Answers (1)

the cyclist on 25 Nov 2014
Edited: the cyclist on 25 Nov 2014
absA = abs(A);
absB = abs(B);
I'm not sure what you mean by "compare ... and return the real value". Larger? Smaller? Difference?
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Jack_111 on 25 Nov 2014
Sorry that my question wasn't phrased well