find ( strcmp ( many_different_elements )

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Dave
Dave 2021-10-14
编辑： Stephen23 2021-10-14
Hello, I want to check if any of the elements of a cell CC with 90 elements are in column2 of a matrix w 10k rows. If so, to retrieve the row location.
CC below has four elements
CC={'AB1', 'AB2', 'AB3' ,'AB4'}
I would use
idloc = find(strcmp(databig{:,2}, 'AB1') | strcmp(databig{:,2}, 'AB2') | strcmp(databig{:,2}, 'AB3') | strcmp(databig{:,2}, 'AB4') )
But was wondering if there's a nicer way than to write 90 times in the find line
  2 个评论
Mitchell Thurston
Mitchell Thurston 2021-10-14
I'm not too experienced with strcmp so there might be a better way, but the easiest way I can think of for this would be
per_index = zeros(numel(CC),1);
for i = 1:length(per_index)
per_index(i) = any( strcmp(databig{:,2}, CC{i}) );
end
idloc = any(per_index)
I would also recommend using "any" for each strcmp instead of find
Mitchell Thurston
Mitchell Thurston 2021-10-14
I just noticed the end of the first sentence also wanted the row location. The general idea should still work.

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回答（2 个）

Ryan
Ryan 2021-10-14
You could create a for loop that checks each element and then do the find outside the four loop for find the rows. Something like this
CC = {'AB1', 'AB2', 'AB3' ,'AB4'};
for ii = 1:length(CC)
idx(:,ii) = strcmp(databig,CC{ii});
end
[idloc,~] = find(idloc);
Stephen23
Stephen23 2021-10-14
编辑：Stephen23 2021-10-14
"But was wondering if there's a nicer way than to write 90 times in the find line"
Of course: forget about repeated STRCMP calls (e.g. in a loop), just use one ISMEMBER call:
https://www.mathworks.com/help/matlab/ref/double.ismember.html
Read its documentation and pay careful attention to the order of its inputs and outputs.
X = ismember(databig(:,2),CC)

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