Calculating results for Partial Sums

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Kyle Donk 2020-1-10

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https://ww2.mathworks.cn/matlabcentral/answers/499783-calculating-results-for-partial-sums

评论： ME 2020-1-18

My question is:

Calculate the result and absolute error for each partial sum: N = 10, 160, and 640. You should use for-loops and not commands like symsum.

I keep on getting weird answes in Matlab and was wondering if my code was missing something:

%(a) Calculate the result and absolute error for each partial sum: N = 10, 160, and 640.

sum=0;

for N=[10 160 640]

for n=1:1:N

y=1/n^2

end

sum=sum+1

error=((pi^2)/6)-sum

end

disp(sum)

PLEASE DO NOT GIVE ME THE COMPLETE ANSWER TO THE QUESTION. I WOULD JUST LIKE AN EXPLANATION OF WHAT I AM DOING WRONG.

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采纳的回答

ME 2020-1-10

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/499783-calculating-results-for-partial-sums#answer_409599

The main problem here is that you arent actually summing the y values as you go along. You are not adding y to the sum like you should, instead you are calculating all of the y values, ignoring them and adding 1 to the sum instead.

You would also probably be better off indexing your sum and error values so that you get one value for each of the Ns you input.

You have asked not to see the code so I haven't included it, but please comment below if you'd like me to add it!

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Image Analyst 2020-1-18

The secondary problems are using sum and error for variable names. Don't use built-in function names for variable names.

ME 2020-1-18

Absolutely, this is a good point. It won’t cause any issues in this simple case but could be more problematic if this was to be built into something larger.

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