How to access double arrays in a cell array?

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Hi everyone,
I have a 1x5 cell array, where each of these 5 columns contains a 20x1 double array.
Now I have the following two questions:
  1. How can I for instance access from this cell array, the first two rows of all the double array it contains (such that I would ideally end up with a 2x5 array of doubles)?
  2. Is there any easy way to construct from this cell array a 20x5 array of doubles, where all rows but the i-th are set to zero?
Many many thanks

Accepted Answer

Stephen23
Stephen23 on 11 Jun 2016
Edited: Stephen23 on 11 Jun 2016
Here are two solutions to your two tasks. First create some fake data:
>> fun = @()randi(9,20,1);
>> C = {fun(),fun(),fun(),fun(),fun()};
1. first two rows of each numeric array:
>> N = 2; % pick the number of rows
>> cell2mat(cellfun(@(c)c(1:N,:),C,'Uni',0))
ans =
8 6 4 7 4
9 1 4 3 8
2. All rows except the Nth are zero:
>> tmp = cell2mat(C);
>> R = 4; % pick the row
>> tmp(R~=(1:size(tmp,1)),:) = 0
tmp =
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
9 9 8 7 5
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
  2 Comments
MiauMiau
MiauMiau on 11 Jun 2016
many many thanks, your answers were really helpful. In the case of 2., is it possible to do the same thing (setting everything except a particular row to zero), while keeping the original format (the 1x5 cell)?
Stephen23
Stephen23 on 12 Jun 2016
@MiauMiau: yes, you should use a for-loop and cell indexing.

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