Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.
Variable limits of integration with Postint
Posted Dec 11, 2009, 12:17 p.m. EST 1 Reply
Please login with a confirmed email address before reporting spam
vyint=postint(fem,'v*(x>xlow)*(x<xup)*(y>ylow)*(y<yup)', ...
where the limits of integration are variable (xlow, etc). When I use this with fixed limits of integration there is no problem. When I switch to variable limits I get an error
??? Java exception occurred:
Exception:
com.femlab.server.MlError: Error using ==> feval
Undefined function or method 'ylow' for input arguments of type 'double'.
(rethrown as com.femlab.jni.FlNativeException)
Messages:
Error using ==> feval
Undefined function or method 'ylow' for input arguments of type 'double'.
Failed to evaluate expression
- Expression: v*(x>xlow)*(x<xup)*(y>ylow)*(y<yup)
Failed to evaluate variable
- Variable: xlow
- Geometry: 1
- Subdomain: 1
Post expr failed
So I guess I need to define xlow, etc. in Comsol as another variable. Is this guess right? If so, how to implement it? How else can this problem be solved?
Thanks
Hello Eric Morales
Your Discussion has gone 30 days without a reply. If you still need help with COMSOL and have an on-subscription license, please visit our Support Center for help.
If you do not hold an on-subscription license, you may find an answer in another Discussion or in the Knowledge Base.
Please login with a confirmed email address before reporting spam
Just starting with COMSOL & MATLAB, I found your question very useful... because it did help me to clarify the syntax to use in integrating over sub-domains.
Effectively, COMSOL doesn't understand your variables "xlow", "xup", "ylow" and "yup". You can parameterize these limits by using an intermediate variable:
xlow = 1; xup = 2;
ylow = 3; yup = 4;
domain = sprintf('u*(x>%d)*(x<%d)*(y>%d)*(y<%d)', xlow, xup, ylow, yup);
postint(fem,domain)
Values 1, 2, 3, and 4 are arbitrary, you can define the four limits according to your problem.
Best regards.