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anyway to cat specific column using horzcat?

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Yu Li
Yu Li 2019년 9월 2일
댓글: Walter Roberson 2019년 9월 2일
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
  댓글 수: 1
Rik
Rik 2019년 9월 2일
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.

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채택된 답변

Walter Roberson
Walter Roberson 2019년 9월 2일
res = cell2mat(cellfun(@(x) x(:,3), A, 'uniform', 0));
  댓글 수: 4
Guillaume
Guillaume 2019년 9월 2일
your answer works
As I commented in dpb's answer, only if the cell array is a row vector.
Walter Roberson
Walter Roberson 2019년 9월 2일
res = cell2mat(cellfun(@(x) x(:,3), A(:).', 'uniform', 0));
This will work even with cell arrays that are column vectors.

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추가 답변 (1개)

Guillaume
Guillaume 2019년 9월 2일
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{:}];

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