CODEWITHSUNDEEP
matlabfor-loopindexing
Benjamin Levy
Benjamin Levy

Reputation: 343

Efficient averaging by indices in matlab

I want to avoid using a loop to create a list of average values from a larger vector. I have the indices in the larger vector for each location in the 'average' vector, but I don't want to wrap this in a loop. Is there a cellfun() method in Matlab to expedite the process. Code and examples follow:

tVector = 10 : 15;
values  = [ 10.1 10.2 10.3 11.4 11.5 11.6 11.7 12.8 12.9 13 13.1 13.2 13.3 13.3 14 14.1 14.2 ];
[ x, n ] = histc( values, tVector );
if any( x ~= 0 )
    indxList = unique( n );
    avgList = NaN * ones( length( indxList ), 1 );
    for k = 1 : length( indxList )
        theseIndxs = find( indxList( k ) == n );
        avgValue = mean( values( theseIndxs ) );
        avgList( indxList( k ) ) = avgValue;
    end
end

The data here are for a trivial example with a small data set. But, my data have much longer lengths, so I'd like to avoid the 'for' loop with possibly the cellfun().

Upvotes: 0

Views: 40

Answers (1)

Luis Mendo
Luis Mendo

Reputation: 112659

Use accumarray with the @mean function:

avgList = accumarray(n(:), values(:), [], @mean);

Upvotes: 1

Related Questions