Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How to draw double integral functions

  1. Feb 14, 2012 #1
    Hi every one!

    I would like to draw a double integral function in related to R and h parameters by below M-File but It does goes wrong!!!
    Is there any one to correct it for me???
    thank you

    syms R h;

    a1 = 0;

    a2 = atan(R./(R+h));

    r1 = h;
    r2 = sqrt(R.^2+(R+h).^2);

    integrand = @(r,a)(h.*sin(a)/((r.^2).*(r.^2+h.^2-2.*r.*h.*cos(a))));
    f = quad2d(integrand,r1,r2,a1,a2);

  2. jcsd
  3. Feb 14, 2012 #2


    User Avatar
    Gold Member

    There's two problems that I can see right away (and perhaps more that I don't see). For one I'm guessing you're trying to make f a function of R and h? But you just leave them as symbolic objects. The second problem is that where you define the integrand, you need an extra "."

    Code (Text):
    integrand = @(r,a)(h.*sin(a)./((r.^2).*(r.^2+h.^2-2.*r.*h.*cos(a))));

    If I understand what you're trying to do correctly then this should do it:
    Code (Text):

    f = @(h,R) quad2d(@(r,a)(h.*sin(a)./((r.^2).*(r.^2+h.^2-2.*r.*h.*cos(a)))),h,sqrt(R.^2+(R+h).^2),0,atan(R./(R+h)));
    When I ran it, there were a bunch of warnings but I think that may be due to a singularity in the integral you're evaluating.
  4. Feb 15, 2012 #3
    Thank you very much.

    your correctness lets the functions be drawn!!!!!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook