Indexing speed of arrays with different index data types

Here is a simple test to prove that integers are
faster than singles or doubles for indexing matlab arrays.

%% test indexing
function untitled

     function test(type)
        % eg : int32(floor(rand(1,100)*100+1))
         k = eval(sprintf('%s(floor(rand(1,100)*100 + 1))', type));
         x = rand(1,100);
         tic
         for i = 1:1e5
             y = x(k);
         end
         toc
         fprintf('%s\n', type);
     end

     test('int32');
     test('uint32');
     test('single');
     test('double');

end

The results are

Elapsed time is 0.194030 seconds.
int32
Elapsed time is 0.195234 seconds.
uint32
Elapsed time is 0.413456 seconds.
single
Elapsed time is 0.804347 seconds.
double

Thus indexing with integers is definately faster.

Vectorize operations based on column and row indicies

Vectorize this

for i = 1:100
  for j = 1:100
    r(i,j) = sqrt(i^2+j^2);
  end
end

becomes

[i,j]=meshgrid(1:100,1:100);
r = sqrt(i.^2+j.^2);