MATLAB: I need to create a loop in which it skips data sets that have a better version of them. e.i if their is an M1 that has an M2 it only reads the M2

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I have to graph massive amounts of csv files but only the newest types of them. A lot of the files have M2, M3, and M4 versions and I only want the newest kind. Is there any way to rid of all the M1-M3 that have better versions?

Best Answer

Use dir() to get the filenames. Then get a new list of filenames where you chop off the last number (assuming they go up only to 9, not to 10 and beyond). Then use ismember to see if the filename occurs twice or more. If it does, get the files, using indexes that ismember tells you, and find out which one has the biggest number. Keep any that occur only once, or if twice, keep just the largest number. Keep these in an output list.
% fileInfo = dir('*.dat');
% fileNames = {fileInfo.name}
% if isempty(fileNames)
%   uiwait(errordlg('No files found'));
%   return;
% end
% Make up sample data for testing.
fileNames = {'file1_m1.dat', 'file1_m2.dat', 'file2_m1.dat', 'file3_m1.dat', 'file4_m1.dat'}
% Create array for filenames without the final character in the base file name.
noVersions = cell(1, length(fileNames));
for k = 1 :length(fileNames)
  % Get base file name without last character.
  [~, thisString, ext] = fileparts(fileNames{k});
  noVersions{k} = thisString(1:end-1);  
end
celldisp(noVersions);
% See if any string is in there more than twice.
uniqueStrings = cell(length(fileNames), 1);
numUnique = 0; % Keep track of how many files we collect so we can truncate the array afterwards.
for k = 1 :length(fileNames)
  thisString = noVersions{k};
  fprintf('Checking for multiple occurrences of %s...\n', thisString);
  [ia, ib] = ismember(thisString, noVersions)
  if ib ~= k
    % This string occurs earlier than element k
    % Overwrite the first occurrence of it with this later version number.
    uniqueStrings{ib} = fileNames{k};
  else
    % This is the first time it appears.  Add it to the list.
    uniqueStrings{k} = fileNames{k};
    numUnique = numUnique + 1;
  end
end
celldisp(uniqueStrings);
% Find out which cells are empty.
emptyCells = find(cellfun(@isempty, uniqueStrings))
% Remove those empty ones to get the final list.
uniqueStrings(emptyCells) = []
The above intuitive brute force method works, though if you wait, I'm sure Andrei will give you a cryptic one-liner (probably using cellfun()) that will do the same thing.
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