Please suggest a method using Vectorization.

I want to do the following operation using vectorization technique of Matlab. I am a novice user of matlab. So please tell me how i can get the following operation done without using the FOR Loop.

x=[1 2 3 4 5 6 7 8 9 10 11 1 2];
for i=1:length(x)
x(i)=((-1)^i)*x(i);
end

Answer 1

[Matt Fig]

Many ways to do it.

Here is one:

x = x.*(-1).^(1:length(x))

and here is another:

x(1:2:end) = -x(1:2:end)

[Vinod S]

Oh..So easy..I didn't know.Thanks Man