Not sure what you are asking, but this may help.
a = 1;
b = 20;
data = a + (b-a).*rand(20,4);
R = corrcoef(data);
RPairs = [nchoosek(1:size(data,2),2), nonzeros(tril(R,-1))];
Where data is your matrix, R is the correlation between each pair of columns, and RPairs represents the column numbers in RPairs(:,1:2) and the corresponding correlation coefficient in RPairs(:,3). Then if you want to calculate the average correlation you simply take the mean of the third column:
MeanR = mean(RPairs(:,3))
Hope this helps
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