How to filter data?

Dear all,

I want to filter a matrix by its date vector. The datevector has the format: dd.mm.yyyy HH:MM:SS. I want to sum up all the data with the same month and year. How can I do that?

Answer 1

[Jan]

dateAsString = {'31.02.2013 11:22:33'; '31.05.2013 11:22:33'}
dateAsVector = datevec(datestr, 'dd.mm.yyyy HH:MM:SS');
yearAndMonth = 100 * dateAsVector(:, 1) + dateAsVector(:, 2);

Now you get values like [201302, 201305] and summing can be done by accumarray directly.

[Walter Roberson]

You would probably not want to use those values as direct subscripts into accumarray: you would probably want to unique() them and use the indices. Otherwise your array is going to end up being up to 240000 long with not many entries used.

[Jan]

You are right, Walter, and even for a FOR loop approach using the indices obtained by UNIQUE is better.