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anyway to cat specific column using horzcat?

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Yu Li
Yu Li 2019 年 9 月 2 日
コメント済み: Walter Roberson 2019 年 9 月 2 日
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 件のコメント
Rik
Rik 2019 年 9 月 2 日
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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採用された回答

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

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その他の回答 (1 件)

Guillaume
Guillaume 2019 年 9 月 2 日
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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