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# Grouping a given matrix into sub matrices

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Abin Krishnan on 14 Feb 2014
Closed: MATLAB Answer Bot on 20 Aug 2021
I have a matrix (1000 X 2) of two columns: first column is the time and the second column is the velocity at the respective time. The time varies from 0 seconds to 0.8 seconds and contain 1000 elements.I need to divide this matrix into several sub matrices in which the time varies by 0.1 seconds. That is, in the first sub matrix ,I need the data of velocities corresponding to time t=0 to t=0.1 seconds.Second sub matrix should contain velocities from t=0.1 to 0.2 seconds. Like that the last sub matrix contains velocities from t= 0.7 to 0.8 seconds.

Azzi Abdelmalek on 14 Feb 2014
Edited: Azzi Abdelmalek on 15 Feb 2014
t=linspace(0,0.8,1000)'
y=rand(1000,1)
idx2=[];
ii=0;
idx1=1;
t(end+1)=0.81;
for k=0.1:0.1:0.8
ii=ii+1;
idx2=find(t>k,1)-1;
out{ii,1}=[t(idx1:idx2) y(idx1:idx2)]
idx1=idx2+1
end

Jos (10584) on 14 Feb 2014
Let M be your matrix with time in the first column
[~, ix] = histc(M(:,1), 0:0.1:0.8)
C = group2cell(M(:,2),ix)
Now, e.g., C{3} contain all the values of M(:,2) for which 0.2 < M(:,1) < 0.3
##### 2 CommentsShowHide 1 older comment
Jos (10584) on 15 Feb 2014
You should download GROUP2CELL from the Matlab File Exchange. It is a user-written function that is not part of of native matlab.
Download the zip-file, expand it, and move the file group2cell.m to a folder on your drive (e.g., D:\UsefulMfiles) and add that folder to the matlab path (File -> Path or something like that)

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