MATLAB: Change sign of every second element of a vector

sign-changevector

Hi,
I want to change the sign of every second element in a vector, starting from element two. I tried the following code. Can someone explain why it does not work and help me to fix it? Thank you!
function newVector = change(v)
    for i = 1:length(v)-1    
        newVector(i) = v(i);
        newVector(i+1) = v(i+1)*-1;
    end
    
    v = newVector
end

Best Answer

A = rand(10,1) ; 
A(2:2:end) = -A(2:2:end)
If you wat to your function, you should use like this: 
function newVector = change(v)
newVector = v ;
for i = 1:length(v)
    if ~mod(i,2)   
        newVector(i) = -v(i);
    end
end
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