Implicit function inside a loop.

Question

Anshuman S 2018-1-21

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/378162-implicit-function-inside-a-loop

评论： Anshuman S 2018-1-21

I want to plot a curve between err and b for different values of b.

I have kept the values of i to be a constant for the inner iteration, and I want to sum up the error ( square )
In 'o' and 'p'for different values of 'i' and finally I want to plot err vs b. such that i get a minimum to this curve at a certain 'b'.

sum =0;
err =0;
for b= 0:1:40
    for i= 0:1:50
f1 = @(o,i) (sind(b+i) + sind(b-o)) -( 1.180/0.04 + sqrt.((1.140/0.04 - 2*sind(b)).^2 - (cosd(b-o)- cosd(b+i)).^2));
f2 = @(p,i) cotd(p-3.34) - cotd(i-1.07) - (1.180/(1.540 - 0.300));
sum = sum + (o - p).^2;
      end
      err = sqrt(sum/50);
    plot (b,err);  
    hold on
  end

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Anshuman S 2018-1-21

I want to use these equations to get the values of 'o' and 'p' which are to be solved for same value of 'i'. Now that i have 'o' and 'p' values in terms of 'b' . I want to sum this for all the 'i's in the inner loop . further when i come out of the loop I want to plot a point (b, err) , the value of b comes from the outer loop. hence i'll get a set of 40 points for err vs b and i'll draw a curve to fit these data.

Thanks

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Answer 1

Walter Roberson 2018-1-21

1
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/378162-implicit-function-inside-a-loop#answer_301039

在 MATLAB Online 中打开

total = 0;
err = 0;
bvals = 0:1:40;
for b = bvals
  subtotal = 0;
  for i= 0:1:50
    f1 = @(o,i) (sind(b+i) + sind(b-o)) -( 1.180/0.04 + sqrt.((1.140/0.04 - 2*sind(b)).^2 - (cosd(b-o)- cosd(b+i)).^2));
    f2 = @(p,i) cotd(p-3.34) - cotd(i-1.07) - (1.180/(1.540 - 0.300));
    subtotal = subtotal + (o - p).^2;
  end
    err = sqrt(subtotal/50);
    plot(bvals,err);  
    hold on
    total = total + subtotal;
  end

But why do you define f1 and f2 when you do not use them? And you have not defined o or p but you try to add their squared difference to the total?

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Anshuman S 2018-1-21

The inner loop varies for 'i' and I want to work (subtotal = subtotal + (o - p).^2) with those values of 'o' and 'p' which come out from the equation f1 and f2 respectively.

Anshuman S 2018-1-21

I want to use these equations to get the values of 'o' and 'p' which are to be solved for same value of 'i'. Now that i have 'o' and 'p' values in terms of 'b' . I want to sum this for all the 'i's in the inner loop . further when i come out of the loop I want to plot a point (b, err) , the value of b comes from the outer loop. hence i'll get a set of 40 points for err vs b and i'll draw a curve to fit these data.

Thanks.

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