MATLAB Language Vectorization Sum, mean, prod & co
Example
Given a random vector
v = rand(10,1);
if you want the sum of its elements, do NOT use a loop
s = 0;
for ii = 1:10
s = s + v(ii);
end
but use the vectorized capability of the sum() function
s = sum(v);
Functions like sum(), mean(), prod() and others, have the ability to operate directly along rows, columns or other dimensions.
For instance, given a random matrix
A = rand(10,10);
the average for each column is
m = mean(A,1);
the average for each row is
m = mean(A,2)
All the functions above work only on one dimension, but what if you want to sum the whole matrix? You could use:
s = sum(sum(A))
But what if have an ND-array? applying sum on sum on sum... don't seem like the best option, instead use the : operator to vectorize your array:
s = sum(A(:))
and this will result in one number which is the sum of all your array, doesn't matter how many dimensions it have.
