how can wirte this integration in matlab.

Question

Pawan Kumar 2018-6-4

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/403846-how-can-wirte-this-integration-in-matlab

评论： Walter Roberson 2018-6-5

int.PNG

file is attached

2 个评论
显示无隐藏无

Walter Roberson 2018-6-5

The solution depends upon the relationship between k and q, and can be further resolved by adding assumptions. Some of the solutions are infinite.

I was certain I had already posted this information.

Walter Roberson 2018-6-5

I was right, I did post it. You asked the question in a different topic as well.. leading to duplicated effort. :(

https://www.mathworks.com/matlabcentral/answers/69221-indefinite-integral-with-matlab#answer_323038

The solution depends on whether k is positive, 0, or negative, and on the relative values of qs and 2*k . In some combinations of circumstances it is undefined. MATLAB is able to resolve some of the combinations if you add appropriate assumptions to the variables, but it is not able to tell you the full conditional resolution under other assumptions.

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Paridhi Yadav 2018-6-4

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/403846-how-can-wirte-this-integration-in-matlab#answer_323042

fun = @(q) q^4/(2*pi*(k^3)*((q + qs)^2)*sqrt(1-(q/2*k)^2));

jdp(k) = integral(fun,0,2*k);

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

Answer 2

Ameer Hamza 2018-6-4

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/403846-how-can-wirte-this-integration-in-matlab#answer_323046

在 MATLAB Online 中打开

If you try to find a closed-form solution, then MATLAB is unable to solve for it for the given integral,

syms k q qs
integrand = 1/(2*pi*k^3*(q+qs)^2*sqrt(1-(q/(2*k))^2))*q^4;
J = int(integrand, q, 0, 2*k)
J =
 int(q^4/(2*k^3*pi*(q + qs)^2*(1 - q^2/(4*k^2))^(1/2)), q, 0, 2*k)

The result is same as the input statement. But if you try to solve it numerically then you can do it as follow

integrand = @(q,qs,k) 1./(2*pi.*k.^3.*(q+qs).^2.*sqrt(1-(q./(2*k)).^2)).*q.^4;
J = @(k, qs) integral(@(q) integrand(q, qs, k), 0, 2*k);
qs = 1;
k = 10;
J(k, qs)
ans =
  0.8855