How to sort array matrix, finding means of output for matching months and reading stations?
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Hi forum,
first post here - hope you guys can help me out:
I have a 4515 x 3 array sorted like this:
In the first column are the IDs for 8 different stations, already sorted (9002, 9002, .... , 9002, 9004, 9004 .... , 9004, 9011, ... and so forth, in the second column are the months of measuring (1,2,3,4,5,6,7,8,9,10,11,12,1,2,3,4 etc) and in the third column are all the individual readings for each station for each month. The data set is for several years, so there will be several loops of all 12 months for each station.
What I need to do is compute the mean of all the readings from the same month for the same station, so I can get a matrix like this:
Jan Feb Mar ...
9002 X
9004
...
so with X being the mean of all the readings from all the Januaries for station 9002.
I'm relatively new to MATLAB, and I don't really have any idea of how to approach this problem... Hope you can help me!
Cheers, Simon
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Accepted Answer
Oleg Komarov
on 18 Sep 2011
Pivot(A(:,[2 1 3]),@mean)
Note that the first column becomes the column header and the second column the row header. Since you want the months on top I reshaped your A.
2 Comments
Oleg Komarov
on 18 Sep 2011
I suspect you have NaNs in you data which propagates.
If you have the stats toolbox use @nanmean.
More Answers (2)
Andrei Bobrov
on 18 Sep 2011
A = sortrows(data);
[a1,~,n] = unique(A(:,1));
out = [0:12;a1 accumarray([n A(:,2)],A(:,3),[n(end) 12],@mean)];
0 Comments
Simon Funder
on 18 Sep 2011
1 Comment
Oleg Komarov
on 18 Sep 2011
Ah sorry commented too late but happy you found the solution to the NaNs.
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