MATLAB: Averaging files with different dates

averagedatestxt

hi! I have files from 1978 to 2009 every 10 days, named as follows:
1978_11.txt
1978_21.txt
. . .
2009_361.txt
2009_365.txt
I would like to average the day 11 of every year and generate a file, then the day 21 and so on, but I dont know how.
I know how to read the files (they are in the same folder, but not how to read the ones I know for the average… Can someone help me please?
thank you for your time

Best Answer

years = 1978:2009
for y = years
    pattern = sprintf('*_%d.txt', y);
    d = dir(pattern);
    Nfiles = numel(d);
    average = 0;
    for i = 1:numel(d)
       filename = d(i).name;
       % read data from filename
       % insert your function here
       % assume that the data is read into variable 'data'
       average = average + 1/Nfiles*data;
    end
    average_filename = sprintf('avg_%d.txt', y);
    % write data to file, e.g., using dlmwrite
    dlmwrite(average_filename, average)
  end
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