Help with a loop that computes at each step

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Lavorizia Vaughn 2021-11-13

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1585584-help-with-a-loop-that-computes-at-each-step

评论： Lavorizia Vaughn 2021-11-14

hi im doing an assignmenr where i have 5 different stepsizes that compose a row vector hs. i have 100/hs steps for which id like to compute the value th2 at each stepsize.

th1=1;
th2=1;
w1=0;
w2=0;
hs(1)=[0.05];
hs(2)=[0.05/2];
hs(3)=[0.05/4];
hs(4)=[0.05/8];
hs(5)=[1/1000];
th2s=[];
????????????
    for i=1:N
        k1= h*fpend(y);
        k2=h*fpend(y + k1/2);
        k3=h*fpend(y + k2/2);
        k4= h*fpend(y + k3);
        y = y + (k1 + 2*k2 + 2*k3 + k4) / 6;
    end
    th2s=[th2s,y(2)]

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Lavorizia Vaughn 2021-11-13

the assignment says,"Run Case 1 in problem 2 with the five stepsizes h = 0.05/2(k−1), k = 1, 2, 3, 4, and h = 0.001. Compute the value of θ2(t = 100) for each stepsize. '

Jan 2021-11-13

The instruction is nonsense: For k=1, the value of h = 0.05/2(k-1) is Inf.

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采纳的回答

Jan 2021-11-13

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1585584-help-with-a-loop-that-computes-at-each-step#answer_830769

在 MATLAB Online 中打开

hs = [0.05, 0.05/2, 0.05/4, 0.05/8, 1/1000];
for k = 1:numel(hs)
   h = hs(k);
   
   N = totalDuration / h; % ???
   y = y0;
   for i = 1:N
        k1 = h * fpend(y);
        k2 = h * fpend(y + k1/2);
        k3 = h * fpend(y + k2/2);
        k4 = h * fpend(y + k3);
        y  = y + (k1 + 2*k2 + 2*k3 + k4) / 6;
   end
   
   th2s(k) = y;  % Why y(2)?
end