I am new to Origin and have been exploring it for curve fitting. I want to enter my own equation to have origin fit to my data. I have tried entering the equation using Origin C as well as an expression and y script, however, I keep getting an error message that says that my parameters are not properly initialized. I have tried various syntaxes but I keep getting the same error. I have included the equation below. Any insight would be greatly appreciated.
Thanks J
y = P1 + P2 / (1+exp(-(x-P4*ln(2^(1/P5)-1)-P3)/P4)) ^ P5
There is no syntax error, the expression you pasted here compiles fine in Origin C....Did you put in suitable initial values for the parameters? And even after putting in initial values you get errors? You may want to try putting bounds on some parameters or fixing some of the parameters to see if the fit converges....this situation could be sensitive to the specific data you are trying to fit.
problem with user defined curve fitting
Posted - 07/10/2009 : 11:42:04 AM
