# How do I store result from a loop into matrix?

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Syed Farez on 6 May 2018
Commented: Syed Farez on 6 May 2018
I have 360 signals to be processed and I'm using STFT for my project. The result for one signal returns:
S = 33x147 double
How do I take only the first column from every 360 signals processed and store it in the same matrix? And how do I make a loop to make it do the same thing but advance to the next column up to the 147th column until I've 147 different matrices of result S?

Ameer Hamza on 6 May 2018
Does your result require 147 matrices at the end? Like this
Result{1} = [first columns of S for all 360 signals] = 33 x 360 matrix
Result{2} = [second columns of S for all 360 signals] = 33 x 360 matrix
....
Result{147} = [147th columns of S for all 360 signals] = 33 x 360 matrix
Syed Farez on 6 May 2018
Yes Ameer, exactly like that brother. Sorry for the misguided question. I've corrected it.

Wick on 6 May 2018
Edited: Wick on 6 May 2018
The first column of S can be indexed S(:,1). The nth is S(:,n);
Instead of making 360 different matrices with different names, we're going to make a three-dimensional array, A, with 360 different pages.
clearvars
num_rows = 33;
num_signals = 360;
num_pages = 147;
A = zeros(num_results, num_signals, num_pages);
for jj = 1:num_signals
% replace the following line with your calculation of S
S = rand(num_results,num_pages);
A(:,jj,:) = reshape(S,num_results,1,num_pages);
end
Each page of A (the different columns from your values of S pasted together into a matrix) can be indexed as:
page_of_columns = A(:,:,n)
where 'n' is the column id you want (from 1 to 147 in your example)

Syed Farez on 6 May 2018
I don't quite understand on the replacing part actually. Could you show me on the code please Sir? :)
Wick on 6 May 2018
clearvars
num_rows = 33;
num_signals = 360;
num_pages = 147;
num_results = 1;
A = zeros(num_results, num_signals, num_pages);
for jj = 1:num_signals
x = Signals_Combined(:,jj);
.....
S = 20*log10(S + 1e-6);
A(:,jj,:) = reshape(S,num_results,1,num_pages);
end
The assumption is that 'S' is different each time based on whatever is above it inside the loop.
Syed Farez on 6 May 2018
Okay. I think I've got it now and it worked like a charm. Just needed a bit troubleshooting. Thank you very much for your help!! You certainly saved me today Sir. :')