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Splitting a signal in MATLAB



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URL: http://projectsqa.com/forum_posts.asp?TID=2489
Printed Date: 11-Dec-2018 at 5:25pm


Topic: Splitting a signal in MATLAB
Posted By: Krishna_Sridhar
Subject: Splitting a signal in MATLAB
Date Posted: 06-Feb-2018 at 6:29pm
I have a signal that is 40 seconds long. I need to split it into 5 equal sections of 8 seconds.

I could do this the long way by:

let my signal = sig
then

subsig1 = sig(1:8*Fs)
subsig2 = sig((8*Fs)+1:16*Fs)
subsig3 = sig((16*Fs)+1:24*Fs)
subsig4 = sig((24*Fs)+1:32*Fs)
subsig5 = sig((32*Fs)+1:40*Fs)

However, I want to do this in a loop. Can anyone help?



Replies:
Posted By: siva
Date Posted: 06-Feb-2018 at 6:30pm
There is nothing wrong with what you did, but if you want to do it in a loop, you could put the signal into a 2D array, rather than separate 1D vectors.


Code ( (Unknown Language)):

for k=1:5
subsig(k,:)=sig( 1+(k-1)*8*Fs : k*8*Fs )
end

Then if you need separate variables you can do what you did in a straightforward way.

Code ( (Unknown Language)):

1. subsig1=subsig(1,:)
2. subsig2=subsig(2,:)
3. subsig3=subsig(3,:)
4. subsig4=subsig(4,:)
5. subsig5=subsig(5,:)

There may be other ways to do it. In the old days, using FORTRAN, we could do this with no work at all by using a COMMON block and associating two variable array names to the same data. One array was declared as a 2D array and the other as a 1D array. The variables names basically shared the same locations in memory so that if you changed the contents of the memory using one variable name, it automatically was changed for the other variable name. I don't know that you can do this in Matlab, but it might be worth checking. Otherwise it's just a matter of pointing to the correct locations, but do it in a way that is efficient in Matlab. Running nested loops and grabbing individual values is very slow in Matlab. It's best to use vector operations as you did originally.


Posted By: Krishna_Sridhar
Date Posted: 06-Feb-2018 at 6:30pm
clear all;
clc;
close all;
% assume the following data
Fs = 100;
sig = 1:40;
count = 0;

for k = 1:8:length(sig);
count = count + 1;
sub_sig = sig(k:k+8-1).*Fs;
fprintf('\n')
fprintf('Set Number %1.0f \n',count);
fprintf('============\n')
fprintf('%4.0i\n',sub_sig);
end


Posted By: Krishna_Sridhar
Date Posted: 06-Feb-2018 at 6:32pm
Sorry I just joined the forum

try this code

clear all;
clc;
close all;
% assume the following data
Fs = 100;
sig = 1:40;
count = 0;

for k = 1:8:length(sig);
count = count + 1;
sub_sig = sig(k:k+8-1).*Fs;
fprintf('\n')
fprintf('Set Number %1.0f \n',count);
fprintf('============\n')
fprintf('%4.0i\n',sub_sig);
end



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