updating/inserting summary array

hi, i have a summary array where it keeps a count of repeated items. e.g

sumarray = {'red',  2; ...
      'blue', 3}

etc. While running a for loop, if a red item appears, I simply want to increment the count to 3 for 'red', if a new category comes in e.g. 'pink' I simply want to add a new row {'pink',1}. What is the most efficient way to implement this?

Thanks.

[Cedric]

Are the colors or words that you want to count stored in a cell array as well (as individual words), or are they in a "stream" of text?

Answer 1

[Image Analyst]

You can use ismember() to check if it's in the list. If it is, increment the second column, if it's not, append it on to the end with a count of 1. See demo code below:

sumarray = {'red',  2; ...
      'blue', 3}
    
% Pick one or the other (red or pink) to test the code.
testWord = 'red'
testWord = 'pink'
column1 = sumarray{:,1}
rowIndex = ismember(testWord, column1, 'rows')
if rowIndex >= 1
  sumarray{rowIndex,2} = sumarray{rowIndex, 2} + 1;
else
  % Not in there yet.  Add it to the end
  sumarray{end+1,1} = testWord;
  sumarray{end,2} = 1;
end

% See what we ended up with
sumarray

[joh]

thank you

Answer 2

[Cedric]

You would have to test, but here is what I guess is an efficient solution:

 colors    = {'red', 'black', 'red', 'green', 'red', 'green', 'red'} ;

 [uc,~,ic] = unique( colors ) ;
 counts    = accumarray( ic, 1 ) ;
 sumarray  = [uc.', num2cell(counts)] ;

For the given dummy set of colors, this outputs

 >> sumarray
 sumarray = 
            'black'    [1]
            'green'    [2]
            'red'      [4]