Origin Ver. and Service Release (Select Help-->About Origin): OriginPro 8 SR0 Operating System: Windows Vista
I am trying to curve fit my data to the Langevin function of the form y = a[coth(b*x) - 1 / (b*x)] where a and b are fitting parameters.
Everything I've tried to write a user defined curve fitting function has ended with utter failure, I'm at a complete loss as to how to get user defined functions working, let alone how write this particular function. Any and all advise would be much appreciated.
The coth() function is not available in Origin C (or in LabTalk), but you can define your function as below (by following how we defined it in the built-in Langevin function shipped with Origin)
double z = b * x;
double cothz = cosh(z)/sinh(z);
y = a * ( cothz - 1/z );
User Defined Curve Fit
Posted - 06/24/2009 : 12:18:56 PM
