# How do I extract specific data from an array inside a cell array using indexing?

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Joel Peeters on 14 Apr 2020
Edited: Ameer Hamza on 14 Apr 2020
So I have a cell array B of size 4*101 in which each cell contains an array of size 1*3, like this:
B = cell([4 101]);
for i = 1:4
for ii = 1:101
B{i,ii} = rand([1 3]);
end
end
And I need to get the third element of the 1*3 arrays from all cells in the top row of the cell array. I can do that using
C = zeros(101,1)
for i = 1:101
C(i) = B{1,i}(3);
end
But since I need to extract this kind of data quite a lot it'd be a lot nicer to be able to do this in one line using indexing. I figured using
C = B{1,:}(3);
Should work but this gives the error
"Expected one output from a curly brace or dot indexing expression, but there were 101 results."
How do I index this so that it works?

Mehmed Saad on 14 Apr 2020
use cellfun
cellfun(@(x) x(3),B(1,:))

Peng Li on 14 Apr 2020
d = cellfun(@(x) x(3), B);
d gives you the third element from all cells. You can index into d to find those that correspond to the first row.
Mehmed Saad on 14 Apr 2020

Ameer Hamza on 14 Apr 2020
Edited: Ameer Hamza on 14 Apr 2020
Use can use basic indexing operations in MATLAB without the need to call any function
B = cell([4 101]);
for i = 1:4
for ii = 1:101
B{i,ii} = rand([1 3]);
end
end
result = [B{1,:}];
result = result(3:3:end);

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