MATLAB: How to access double arrays in a cell array

cell arraysdouble

Hi everyone,
I have a 1×5 cell array, where each of these 5 columns contains a 20×1 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 2×5 array of doubles)?
  2. Is there any easy way to construct from this cell array a 20×5 array of doubles, where all rows but the i-th are set to zero?
Many many thanks

Best Answer

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
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