How I can perform a loop in order to calculate multiple means in a matrix based on multiple values?

Hello Matlab community! I am learning how to perform loops!

I am working with multiple years of meteorological information, and I would like to perform a loop in order to compute the mean by each hour of record, and after that concatenate every result in a single matrix. I have to say that the records are at hour 0, 3, 6, 9, 12, 15, 18 and 21.

I have been working in the next code, but without results:

      m3=zeros(8,100);

      interval=0:3:21; %these are the hours which the mean would be calculated

      for i=1:8
      XMINHOUR(i)=XMIN(find(XMIN(:,1) == interval(i)),:); 
      D_0(i)=XMINHOUR;
      m3=mean(D_0);

      end

I have attached to the present message the data (variable XMIN)

Thanks in advance for your support!

Miguel

I wanted to ask you

Answer 1

[Andrei Bobrov]

>> [g,v] = findgroups(XMIN(:,1));
>> out = splitapply(@mean,XMIN,g);

or

[ii,jj] = ndgrid(findgroups(XMIN(:,1)),1:size(XMIN,2));
out = accumarray([ii(:),jj(:)],XMIN(:),[],@mean);

[Miguel L]

Hello Andrei!

I really appreciate your help! But I wanna ask you if there is an equivalent of "findgroups" or "splitapply" commands for MATLAB 2011 (my current version).

Best,

Miguel

[Andrei Bobrov]

[~,~,g] = unique(XMIN(:,1));
[ii,jj] = ndgrid(g,1:size(XMIN,2));
out = accumarray([ii(:),jj(:)],XMIN(:),[],@mean);