Hello, I have a data set which contains a value for a number of stations during some years (station, date, value). Data for some days is missing. I need to create a column with annual average value per station. I appreciate your help.
station date value average(yearly per station)
1 2001/1/1 2 2
1 2001/1/3 1 2
1 2001/1/5 3 2
2 2001/1/1 2 2.5
2 2001/1/4 3 2.5
1 2002/1/2 2 1.5
1 2002/1/6 1 1.5
2 2002/1/1 2 2.5
2 2002/1/2 3 2.5 . .
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It looks like the fourth column is what you want to calculate. If so, this will do the job, assuming that you have the first three columns as station, date, and value (numeric vectors except date which is a cell array of strings)
% get the years from the date strings dv = datevec(date); year = dv(:,1);
% get all combinations of station & year [stlist,yrlist] = meshgrid(unique(station),unique(year));
% allocate space for the calculated average avg = zeros(size(station));
% loop over every station/year combination for k = 1:numel(stlist) % find the location of this combination in the data set idx = (year == yrlist(k)) & (station == stlist(k)); % calculate the mean avg(idx) = mean(value(idx)); end
This could probably be simplified with prior knowledge of the station numbers and years.
EDIT TO ADD: Given your comment above, ignore the first couple of lines -- you already have year.