How to filter and group data in matlab

Hello,

I try to group data in matlab by doing:

Consider a dataset like the following:

data = dataset;
data.groups_a = [1;1;2;1;2;2;2]; 
data.groups_b = [7;8;9;7;8;9;9];
data.values   = [103;187;261;366;271;287;311]; 

%%Now let's sum up the values for each group in groups_a

[groups_a,~,ICa] = unique(data.groups_a);
[groups_b,~,ICb] = unique(data.groups_b);

groupped_by_a  = accumarray(ICa,data.values,[],@nansum);

So this works excellent is quite fast even for large datasets. But how can I now retrieve the values grouped by groups_a AND groups_b? So my matrix should be:

x = zeros(length(groups_a),length(groups_b));

Example:

x(1,1) should be the sum of all values that are in group_a == 1 and group_b == 7. So the correct entry would be x(1,1) = 103 + 366;

Can somebody may point me to the solution? Thank you very much beforehand!

Regards!

Answer 1

[Walter Roberson]

accumarray( [ICa, ICb], data.values, [], @nansum)

[Léon]

So close ;)

Thank you very much !