How to access double arrays in a cell array?

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

Answer 1

[Stephen23]

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

[MiauMiau]

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]

@MiauMiau: yes, you should use a for-loop and cell indexing.