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How to order values within a cell array more efficiently??

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I have a 3x12 cell array called "ratings"
ratings= {'AAA','AA','A','A-','BBB-','BB+','BB','BB-','B+','B','B-','CCC+';
'A','A-','AA','AAA','B','B+','B-','BB','BB+','BB-','BBB-','CCC+';
1,1,1,3,11,16,18,1,1,17,16,14};
  • The first row of the array has the ratings in the desired order
  • The second row has the ratings disordered
  • The third row contains a number associated with the ratings in the second row
I wrote the following code:
orderedratings=cell(1,length(ratings))
for i=1:length(ratings);
for j=1:length(ratings)
if strcmp(ratings(1,i),ratings(2,j))==1
orderedratings(i)=ratings(3,j);
end
end
end
and it allows me to reorder the third row in respect to the ordered first row, such that:
orderedratings={1,6,8,2,18,3,1,21,17,12,10,1}
Is there a way to do the same more efficiently, or another way without "for" conditionals?? It is very much appreciated a different appoach.
Antonio Espana
  2 Comments
Ben Petschel
Ben Petschel on 15 Nov 2013
If I run your code I get a different result:
orderedratings = { 3, 1, 1, 1, 16, 1, 1, 17, 16, 11, 18, 14}
Not sure how you obtained {1,6,8,...}
Antonio Espana
Antonio Espana on 15 Nov 2013
Hi Ben thanks for the heads up, you are right the result i wrote is completely wrong and your result is the right one. It is not a problem with the code but a blunder on my side cause i wrote the result of a different ratings array.

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Accepted Answer

Ben Petschel
Ben Petschel on 15 Nov 2013
The following should work regardless of the ordering of the two rows:
[~,idx] = ismember(ratings(1,:),ratings(2,:));
orderedratings = ratings(3,idx)
  1 Comment
Antonio Espana
Antonio Espana on 15 Nov 2013
Hi Ben
Also tested this code and is very fast and elegant, with all this ideas i can get rid of a lot of conditionals thanks.
Antonio

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More Answers (3)

Simon
Simon on 14 Nov 2013
Hi!
orderedratings = cellfun(@(x) ratings{3,x}, ...
cellfun(@(x) strcmp(x,ratings(2,:)), ratings(1,:), 'UniformOutput', false));
It takes about 2/3 of the time, but it is not very easy to read ...
  7 Comments
Simon
Simon on 15 Nov 2013
orderedratings{1,7} is a 1x2 cell because the 7th element in the first row of ratings 'BB' is found in the 8th and 10th element of the second row, while the 8th element in the first row of ratings 'BB-' wasn't found at all in the second row. Great, isn't it? ;-)
Antonio Espana
Antonio Espana on 15 Nov 2013
Thank you very much i overlooked the fact that your example had two cells with the same value whereas my normal ratings arrays never have repeated values. Now, that could be useful way to control my arrays hehe.
Antonio

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Azzi Abdelmalek
Azzi Abdelmalek on 14 Nov 2013
Edited: Azzi Abdelmalek on 15 Nov 2013
[~,~,idx]=unique(ratings(1,:));
out=ratings(3,idx)
ADD
If the second row is not sorted
[idx2,idx2]=sort(ratings(2,:));
[~,~,idx12]=unique(ratings(1,:));
idx12=idx2(idx12);
out=ratings(3,idx12);
  5 Comments
Antonio Espana
Antonio Espana on 15 Nov 2013
Silly me now i get what you mean by sorted, my second row is always sorted because is the result of another implementation of the unique function in another part of my code, i scrambled the second row a bit and with the ADD code still manages to work. Thanks
Antonio

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Azzi Abdelmalek
Azzi Abdelmalek on 15 Nov 2013
In case the second row is not sorted
[idx1,idx1]=sort(ratings(1,:));
[idx2,idx2]=sort(ratings(2,:));
[kk,kk]=sort(idx2);
[idx,idx]=sort(idx1(kk));
orderedratings = ratings(3,idx);%
  3 Comments
Azzi Abdelmalek
Azzi Abdelmalek on 15 Nov 2013
After speed test, this code seems slightly faster then my previous answer

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