Triangle_wave question

Question

Qingchuan Lyu 2018-6-29

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/408122-triangle_wave-question

回答： Star Strider 2018-6-29

In this question, I have used the debugging tool in matlab and checked step by step. Everything looks fine. However, when I test my codes in the whole, everything seems broken. Could someone give me a hint how to fix my codes? Previously, someone has posted his codes for the same question, but my codes do not have the same issues. In particular, when n=10, the first element of v should be 0, but i got something different. The weird thing is that i did get 0 when debugging.

if true
  % function v = triangle_wave(n)
me=zeros(1,n+1);
v=zeros(1,1001);
for t = 0:4*pi
  for i=1:1001
      for k = 0:n
       me(k+1) = ((-1).^k)*sin(2.*k.*t+t)./(2.*k+1).^2;
      end
  v(i)=sum(me);
   k = k+1;
t=t+4*pi/1000;
i=i+1;
  end
end
end

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Answer 1

Star Strider 2018-6-29

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You have coded the essential loop correctly. The problem is that you overloaded your code with a lot of irrelevant items. I would increase the resolution of ‘t’, and simply use the ‘k’ loop:

t = linspace(0,4*pi);
n = 100;
me = zeros(n+1, numel(t));
for k = 0:n
    me(k+1,:) = ((-1).^k)*sin(2.*k.*t+t)./(2.*k+1).^2;
end
me = sum(me);
figure
plot(t, me)