how to average seasonly?

i have data set 141x49x300 (longitude,latitude,time), it contains data monthly average from 1995-2019. which mean 141x49x1 mean jan 1995 and 141x49x300 mean december 2019.

how do make average data every three month (dec, jan, feb) (mar, apr, may) and so on?

thanks

Answer 1

[dpb]

This one is cute... :) Unfortunately, timetable won't accept a 2D array by row so have to do things directly...

t=linspace(datetime(1995,1,1),datetime(1995,12,31),300).';          % 300 elements between above start, stop
[r,c,p]=size(A);                                                    % sizes of data, A
M=(splitapply(@mean,reshape(A,r*c,[]).',findgroups(quarter(t))));   % compute means by quarter by columns
M=reshape(M.',r,c,[]);                                              % reshape back to rxcx4

Substitute your real time vector for t, of course.

I did a trial here to check ordering...

t=linspace(datetime(1995,1,1),datetime(1995,12,31)).';  % only 100 instead of 300
A=randi([50 100],5,5,100);                              % dummy 5x5 data
M=(splitapply(@mean,reshape(A,25,100).',findgroups(quarter(t)))); % compute means 2D

>> M(:,1:3)            % small piece to look at to check
ans =
   78.4400   76.6000   75.3200
   76.3200   73.2400   74.7200
   71.6800   76.7200   83.7200
   80.6000   74.3600   74.8000
>> 
>> MM=reshape(M.',5,5,4);
>> whos MM
  Name      Size             Bytes  Class     Attributes

  MM        5x5x4              800  double              

>> squeeze(MM(1,1,:))
ans =
         78.44
         76.32
         71.68
         80.60
>> squeeze(MM(2,1,:))
ans =
         76.60
         73.24
         76.72
         74.36
>>