MATLAB: Find the mean for each category and summarize it

categoricalcategoryMATLABmeansummarizesummary

Hello,
i have a table which consists of the following data
Category value1 value2
1 20 33
3 23 43
2 50 32
4 13 32
4 30 15
3 33 23
1 60 12
2 24 43
i want to find the modulus mean value for each unique category and summarize them, e.g.
Category value1 value2
1 23.54 15.33
2 35.44 42.55
3 29.33 33.32
4 44.34 23.44
can anyone help me with this?

Best Answer

For a numeric array, you can use the accumarray function to do this. That function is a bit tricky to learn the power of, and is also not really set up for operating on a matrix of data. However, Sean de Wolski provided a nice solution here, which I borrow below.
For a table, it is simpler. You can use grouping variables in the varfun function.
I illustrate both below.
M = [1 20 33
     3 23 43
     2 50 32
     4 13 32
     4 30 15
     3 33 23
     1 60 12
     2 24 43];
% On the original matrix
[~,~,c] = unique(M(:,1));
data = M(:,[2 3]);
sz = size(data);
meanByCategoryForMatrix = accumarray([repmat(c,sz(2),1), repelem((1:sz(2))',sz(1),1)],data(:),[],@mean)
% Or put them in a table first
Category = M(:,1);
value1 = M(:,2);
value2 = M(:,3);
tbl = table(Category,value1,value2);
meanByCategoryForTable = varfun(@mean,tbl,'GroupingVariables','Category','InputVariables',{'value1','value2'})
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