How to filter data?

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Thor 2013-1-16

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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?

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Answer 1

Jan 2013-1-16

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https://ww2.mathworks.cn/matlabcentral/answers/58980-how-to-filter-data#answer_71379

在 MATLAB Online 中打开

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.

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Walter Roberson 2013-1-16

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.