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How to conditionally delete columns in a cell array

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Blue on 29 Apr 2020
Commented: Star Strider on 29 Apr 2020
I have a simple cell array that look like this:
input = {'A','B','A','A','A','A','A','A'; 'A','A','B','A','A','A','A','A'; 'A','A','A','A','A','A','A','A'}
What I want to do is to simply delete all the columns that dont contains 'B' but only those to the right hand side of the last column that contains a 'B'.
In other words the ouput would look like this:
ouput = {'A','B','A'; 'A','A','B'; 'A','A','A'}
How would I do that ?
Thank you,

Accepted Answer

Star Strider
Star Strider on 29 Apr 2020
Try this:
inputc = {'A','B','A','A','A','A','A','A'; 'A','A','B','A','A','A','A','A'; 'A','A','A','A','A','A','A','A'};
isB = cell2mat(cellfun(@(x)ismember('B',x), inputc, 'Uni',0));
[r,c] = find(isB, 1, 'last');
outputc = inputc(:,1:c)
outputc =
3×3 cell array
{'A'} {'B'} {'A'}
{'A'} {'A'} {'B'}
{'A'} {'A'} {'A'}
I could have combined ‘isB’ and the find call in one line, however breaking it into two lines is easier to understand.

More Answers (1)

Guillaume on 29 Apr 2020
If your cell array is indeed a cell array of single characters, then you'd be better off storing it as a char matrix:
input = cell2mat(input);
In which case:
[~, lastc] = max(input == 'B', [], 2);
output = input(:, 1:max(lastc))


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