anyway to cat specific column using horzcat?

2 views (last 30 days)
Hi:
I have a cell array, the size is not determined, but each array is a 1000*3 matrix.
I want to merge the 3rd column of each array into a new matrix, is there anyway to do it?
below are what I have tried:
A{1}=rand(1000,3);
A{2}=rand(1000,3);
A{3}=rand(1000,3);
result= horzcat(A{:}(:,3))
or result= [A{:}(:,3)];
but Matlab reported error: Expected one output from a curly brace or dot indexing expression, but there were 3 results.
Thanks!
Yu
  1 Comment
Rik
Rik on 2 Sep 2019
As far as I'm aware, there is currently no way to do this directly in Matlab.
What you could do in this specific case is to cat A to the third dimension, and then select your data from the 3D array.

Sign in to comment.

Accepted Answer

Walter Roberson
Walter Roberson on 2 Sep 2019
res = cell2mat(cellfun(@(x) x(:,3), A, 'uniform', 0));
  4 Comments
Walter Roberson
Walter Roberson on 2 Sep 2019
res = cell2mat(cellfun(@(x) x(:,3), A(:).', 'uniform', 0));
This will work even with cell arrays that are column vectors.

Sign in to comment.

More Answers (1)

Guillaume
Guillaume on 2 Sep 2019
As others have said, no you can't do that with a single statement.
Assuming a cell array of any shape and size, rik's suggestion is probably the shortest to write:
result = cat(3, yourcellarray{:});
result = squeeze(result(:, 3, :));
The other option is cellfun indeed but without cell2mat if the cell array is not a row vector:
result = cellfun(@(m) m(:, 3), 'UniformOutput', false);
result = [result{:}];

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!