Nonlinear Regression
I am trying to fit a one predictor (x) nonlinear model. Below some value of x my model form is different than above that x. Using an conditional if in the formula, I am setting that x value to a parameter to be estimated:
Parameter({theta1 = 1, theta2 = 1, b2 = 20, b3 = 1, b4 = 1},
If( :Pore Size - b2 < 0, 1 / (1 + theta1 * Exp(theta2 * ( :Pore Size - 10))),
1 / (1 + b3 * Exp(b4 * ( :Pore Size - 10)))))
But when I run nonlinear with this model, JMP will not vary b2--it keeps it fixed.
Any help out there?
