# Create a matrix on the basis of other matrix

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luca on 14 Oct 2019
Commented: Fabio Freschi on 15 Oct 2019
Hi given a vector
SPI= [2 3 4 8 11 13 14 15 16 19 20];
and the array
AA= [1 2 3 4 0 11 15;
0 0 0 8 13 16 0;
0 0 0 0 0 18 0;
0 0 0 0 0 19 0;
0 0 0 0 0 20 0];
I want to create a matrix DD that is AA but with just the element inside SPI. So:
DD = [ 2 3 4 0 11 15;
0 0 8 13 16 0;
0 0 0 0 0 0;
0 0 0 0 19 0;
0 0 0 0 20 0];
may someone help me?
##### 2 CommentsShowHide 1 older comment
luca on 14 Oct 2019
the array SPI could vary and contain all the elements of AA, that instead is fixed. So depending on the value inside SPI I want to derive DD.
Sorry for the third column, was my mistake! now it's fixed

Fabio Freschi on 14 Oct 2019
Edited: Fabio Freschi on 14 Oct 2019
SPI = [2 3 4 8 11 13 14 15 16 18 19 20];
AA = [1 2 3 4 0 11 14 15;
0 0 0 8 13 16 0 0;
0 0 0 0 0 0 0 0;
0 0 0 0 0 19 0 0;
0 0 0 0 0 20 0 0];
% matrix DD with zeros
% now you can filter out the rows and cols of all zeros
DD = DD(:,any(iMask,1)); % cols filter
DD = DD(any(iMask,2),:); % rows filter
Fabio Freschi on 15 Oct 2019
Me neither! but I kept all steps separated to that the OP can pick the parts of his choice

R2019b

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