Get means for nested categorical variables
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Assuming you have the following table:
site = {'1','1','1','1','2','2','2','2','3','3','3','3'}';
site = categorical(site);
days = {'0','0','45','45','0','0','36','36','0','0','67','67'}';
days = categorical(days);
var = [23,45,67,21,42,87,84,65,12,77,42,90]';
T = table(site,days,var);
how do I make a new table T1 with each unique value of site and days, and the means of var over the days category? e.g. T1 = table(site,days,meanvar)
采纳的回答
Akira Agata
2018-3-14
Please try the following:
[group,site,days] = findgroups(T.site,T.days);
meanvar = splitapply(@mean,T.var,group);
T1 = table(site,days,meanvar);
更多回答（2 个）
Peter Perkins
2018-3-15
Another possibility:
>> T2 = varfun(@mean,T,'GroupingVariables',{'site' 'days'})
T2 =
6×4 table
site days GroupCount mean_var
____ ____ __________ ________
1 0 2 34
1 45 2 44
2 0 2 64.5
2 36 2 74.5
3 0 2 44.5
3 67 2 66
By the way, "1", "2", etc. are perhaps perfectly good category names for the site variable (as long as you remember that the values are text, and not the numeric values 1, 2, etc), but it seems like days is a numeric count. If that's true, there's no particular reason why you can't just leave it as numeric. The above code, and indeed the version usig findgroups/splitapply, continues to work.
Razvan Carbunescu
2018-3-16
>> GT = groupsummary(T,{'site','days'},'mean','var')
GT =
6×4 table
site days GroupCount mean_var
____ ____ __________ ________
1 0 2 34
1 45 2 44
2 0 2 64.5
2 36 2 74.5
3 0 2 44.5
3 67 2 66
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