calculate the accumulation of a variable over time within a loop?
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Hello,
I have evaporation as daily values (m). I have calculated the weighted fieldmean, which gives me a vector with length = no. of days. However, I would like to display these values as monthly sums.
How can I do this in a loop?
For example:
newsum(1) = nansum(data(1:30)) and so forth...
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dpb
2014-9-17
Do you have a corresponding date/day of month vector or does the series simply begin at a known date? And, of course, year to know if leap year or not...
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Sean de Wolski
2014-9-17
Once you get the month data, the code will be almost identical to this answer:
Instead of @std, you'll want to pass in @sum
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dpb
2014-9-17
编辑:dpb
2014-9-17
... to calculate 3-month sums...
There it's simpler to use another Matlab "trick" of recognizing and utilizing internal storage order and Matlab's handling of arrays. Generate the vector of monthly sums as above then to group by threes reshape and sum over the reshaped array and recast back...
mnthsum=accumarray(... % the monthly sums as above
threemnth=sum(reshape(mnthsum,3,[])).'; % sum over columns of 3 row/each
The above relies on the linear storage order and that Matlab orders arrays/matrices in column-major order and the default action of functions such as sum is to operate over columns. This "trick" is useful for any such operation over a given evenly-divisible subset of any array.
ADDENDUM
If it's decided that the monthly sums aren't needed any longer, the above can be done in place, of course...
mnthsum=sum(reshape(mnthsum,3,[])).';
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