Accelerating MATLAB Performance

258 Accelerating MATLAB

®

Performance

In the fourth alternative, we use matrix multiplication to obtain the array indices in

order to do everything in a single line of code:

A([1:size(A,1)]' * ones(1,2),

[1:size(A,2)]' * ones(1,3))

5.4.1 A Simple Example

Consider the following problem: we have a numeric matrix A and wish to normalize each

row independently, so that each row sums to 1. We can loop over all data rows, sum the

values in each row, and then divide each element in that row with its total:

A = rand(1e6,3); % 1Mx3 test data

% loop over all rows

for row = 1 : size(A, 1)

% sum all elements in the "i"th row

total = 0;

for col ...