Change sign of every second element of a vector

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

[madhan ravi]

@KSSV: Why did you delete my comment ?

Answer 1

[KSSV]

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

[madhan ravi]

KSSV why did you delete my comment?

[am]

Great, that did the job finely!

[KSSV]

@am You can see that I have a given a snippet using loop also..you may compare your code and the present one and you can analyse the problem in your code. Like this you can learn on your own. Coding need not to be explained....it should be learnt on your own.