Is it possible to vectorize this loop?

A = rand(1, 100);
B = rand(1, 100);
w = 0;
for i = 1:length(A)
    w = w +  A(i).*B;
end

Answer 1

[Stephan]

w_new = (sum(w +  A.*B(:),2))';

[Adam Frej]

Good answer. It can be simplified to:

w_new = (sum(A'*B))

Answer 2

[Jan]

A = rand(1, 1000);
B = rand(1, 1000);
tic
for k = 1:1000
  w = 0;
  for i = 1:length(A)
     w = w +  A(i).*B;
  end
end
toc

tic
for k = 1:1000
   w = (sum(A .* B(:),2))';
end
toc

tic
w = 0;
for k = 1:1000
   w = sum(A' * B);
end
toc

I get the timings (Matlab online!):

0.34 seconds
0.69 seconds
0.41 seconds

So check it on your machine is the vectorization is an advantage.