This may be a naïve question but I am confused about the 4PL equation used by jmp in curve fitting. I have a dataset of two variable and I choose: analyze>modeling>nonlinear
Then I plot the data and the red fit-curve button gives the option: Sigmoid curves>logistic curves>Fit logistic 4P
Now my question is; the equation used by jmp is f(x).
Yes it seems everything after the equals sign gets deleted. Thanks for replying. My question concerns the logistic 4P fit in sasjmp. The equation used for this is not the same as for 4 parameter logistic fits used in various applications software I am used to. Is it just not the same model or is there some mathematical point I am missing? Usually 4PL is described as y equals ((A-D)/(1+((x/C)))+D
Yes, the parameterization you give is different than the one used in JMP. The following is a reasonable discussion of the two parameterizations. JMP uses the one that it does to avoid having a parameter in an exponent, which makes estimation more difficult.