integration using quadgk() in the complex plane

Hi, I am trying to do an integration in the complex plane, and the upper limit of interval need to be complex infinity. But when I try to use quadgk(Fun,2,1i*inf), I will get the following message:

??? Error using ==> quadgk at 153 Contour endpoints and waypoints must be finite.

Can anyone help?

Answer 1

[Mike Hosea]

I'm going to assume this is a homework problem. Complex integrals generally depend on the path chosen. Here you want to go from 2+0i to the 0+inf*1i, but what path do you intend to take? Define a path that is parameterized by a real variable, substitute into your complex path integral, and evaluate the resulting integral (which will be over a real interval).

[Liping]

Hey Mike,

Thanks for your answer. I understand what you mean. But I still wander if there is any simple way to do this? I have 16 functions, so it is not that easy to transform the integrand to the real interval.

[Bjorn Gustavsson]

If I recall my complex analysis (doubtful about the time-waste to type...) you have to look at the poles of your functions and choose the integration paths with their position in mind.