I don't know what retmap is (did you mean repmat?)
Anyway, this normalizes the matrix by rows as you described,
% sample data
data = rand(20) .* randi(100,20,1)
% Normalize rows of 'data' so each row sums to 1
dataNorm = data./sum(data,2)
% confirm by adding values in each row
% The asser() will throw an error if any row does
% sum to 1, leaving room for precision error.
addedRows = sum(dataNorm,2);
assert(all(abs(addedRows-1)<1E10), 'Santify check failed: normalization is incorrect.')
