Trying to use summation notation in a for loop

Question

James Crowe 2017-10-26

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/363380-trying-to-use-summation-notation-in-a-for-loop

评论： Birdman 2017-10-26

Hi I'm trying to estimate a cos graph using summation between 1:1, 1:2, 1:3, 1:4 and 1:5. How would I plot each of these individually?

Could someone help me out please! Thank you

    x = -pi:0.1:pi;
ye = cos (x);
n = 5;
summe = 0.0;
for i = 1:n
    summe = summe +((-1).^(i)).*((x.^(2.*i))./(factorial(2.*i)));
end 
    plot (x, summe);

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Answer 1

Birdman 2017-10-26

1
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https://ww2.mathworks.cn/matlabcentral/answers/363380-trying-to-use-summation-notation-in-a-for-loop#answer_287870

编辑：Birdman 2017-10-26

在 MATLAB Online 中打开

Firstly, this code will give an error since X vector is 1x63 and n is 1x5. There will be a size mismatch. You have to correct this. Use the following code.

x = -pi:0.1:pi;
ye = cos (x);
n = length(x);%has to be same size with x
i = 1:n;
for k = 1:n
  summe = summe +((-1).^(i)).*((x.^(2.*i))./(factorial(2.*i)));
end
plot(x,summe)

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James Crowe 2017-10-26

It's for some coursework I've been told to use a for loop

Birdman 2017-10-26

I have corrected it.

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Answer 2

KSSV 2017-10-26

1
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/363380-trying-to-use-summation-notation-in-a-for-loop#answer_287868

在 MATLAB Online 中打开

x = -pi:0.1:pi;
ye = cos (x);
n = length(x);
i = 1:n;
summe = 0.0;
for k = 1:n
    summe = summe +((-1).^(i)).*((x.^(2.*i))./(factorial(2.*i)));
end
plot (x, summe);