Change sign of every second element of a vector

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am 2019-3-22

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https://ww2.mathworks.cn/matlabcentral/answers/451629-change-sign-of-every-second-element-of-a-vector

编辑： madhan ravi 2019-3-22

采纳的回答： KSSV

在 MATLAB Online 中打开

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

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madhan ravi 2019-3-22

编辑：madhan ravi 2019-3-22

@KSSV: Why did you delete my comment ?

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采纳的回答

KSSV 2019-3-22

1
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/451629-change-sign-of-every-second-element-of-a-vector#answer_366761

编辑：KSSV 2019-3-22

在 MATLAB Online 中打开

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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am 2019-3-22

Great, that did the job finely!

KSSV 2019-3-22

@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.

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