No result for while loop Statement

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Zhuoying Lin 2017-11-14

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/366905-no-result-for-while-loop-statement

评论： Guillaume 2017-11-15

Matlab remains busy running my script forever, what's wrong with my script?

 n=1;
while abs(pi-sum(4./((2*(1:n)-1)*(-1).^(n+1))))>=0.001
      n=n+1;   
       sum(4./((2*(1:n)-1)*(-1).^(n+1)));
end
fprintf('The approximation using Leibniz''s formula falls within 0,001 of pi when it equals to')
fprintf('%.5f with n equls %d\n\n',sum(4./((2*(1:n)-1)*(-1).^(n+1))),n)
    end

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回答（1 个）

Guillaume 2017-11-14

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/366905-no-result-for-while-loop-statement#answer_291010

Well, if you hadn't put a semicolon at the end of the line sum(...); effectively making it useless by suppressing the output, you would have seen that as n increases your sum gets further and further away from π instead of converging towards it.

That would be because you've implemented the formula incorrectly, in particular the (-1).^(n+1) which should be a vector. Manually testing each term of your formula for a few values of n should have shown you that.

Also note that you're recalculating all the terms of the expression each time you increase n, so your algorithm is not going to be particularly fast. I suppose it doesn't matter as it would converge quickly if the formula had been implemented right.