indexing cell array of arrays

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John Petersen
John Petersen on 9 Aug 2013
I have a cell array with M arrays of [Nx1] elements in each cell. How do I create a cell array with the same M arrays but with the first K elements of each cell?

Accepted Answer

Evan
Evan on 9 Aug 2013
Edited: Evan on 9 Aug 2013
cellfun(@(x)x(1:K),C,'uni',0) %Where C is your original cell array
  3 Comments
Evan
Evan on 10 Aug 2013
Edited: Evan on 10 Aug 2013
Note that, when using implicit functions with cellfun, operation will often be slower than a FOR LOOP would be (this is because cellfun has to do the looping anyway, plus some overhead). So, in cases where you're working with large arrays and/or operation time is quite important, my method above is not ideal.

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More Answers (3)

Azzi Abdelmalek
Azzi Abdelmalek on 9 Aug 2013
for k=1:numel(A)
A{k}=A{k}(1:4);
end
  2 Comments
Evan
Evan on 10 Aug 2013
Edited: Evan on 12 Aug 2013
Yes. I'll make a comment on my answer noting that Azzi's is preferred in all cases except where you want a quick and messy answer.

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Azzi Abdelmalek
Azzi Abdelmalek on 9 Aug 2013
If A is your cell array
cellfun(@(x) x(1:k),A,'un',0)

Daniel Shub
Daniel Shub on 9 Aug 2013
Edited: Daniel Shub on 23 Aug 2013
It is not clear why you have a cell array with each element having Nx1 data, but if all the Nx1 arrays are the same type you can use CELL2MAT. Sticking with the one line answers:
mat2cell(subsref(cell2mat(x), struct('type', {'()'}, 'subs', {{1:K, ':'}})), K, ones(M, 1));
where x is your cell array.
If the M Nx1 arrays are different classes, for example from the output of
data = textscan(fileID,'%s %s %d %f %f');
I would convert my cell array into a structure array with meaningful field names
tempCellMat = cellfun(@(x)mat2cell(x, ones(length(x), 1), 1), data, 'UniformOutput', false);
structArray = cell2struct([tempCellMat{:}], {'Name','dateStr','age','weight','height'}, 2);
You can then do structArray(1:k).
  2 Comments
Daniel Shub
Daniel Shub on 23 Aug 2013
Ahh, so each of your M arrays of [Nx1] elements is of a potentially different class. This means you cannot use CELL2MAT and my answer will not work.... See my edit.

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