MATLAB: Averaging time-series data without loops?

Question

I have measured a handful of variables in 30 minute intervals. Time stamps are available in datevec or datenum format. I want to calculate ...

Answer 1

Considering that datevec() output is stored in tvec and data in x, group with unique(...,'rows') and accumulate with accumarray():

% Group by day
[unDates, ~, subs] = unique(tvec(:,1:3),'rows');

% Accumulate by day
[unDates accumarray(subs, x, [], @mean)]

% Similarly by hour
[unHours, ~, subs] = unique(tvec(:,4:5),'rows');
[unHours accumarray(subs, x, [], @mean)]