how to enter the initial value for parameters when fit a nonlinear model

desertrose

Hello,  I have a question about nonlinear model fit. For example, here is my data set is attached.

x   y

0.861	1.000
0.775	1.082
0.686	1.007
0.896	0.985
0.796	1.007
0.690	1.000
0.917	0.971
0.807	0.977
0.722	0.970
0.714	0.898
0.587	0.774
0.456	0.564
0.448	0.384
0.321	0.191
0.201	0.115

I know it fits this model.

Y=1/(1+A*(EXP(B*X))

When I use JMP 10 to fit the model, I am stuck at the step what number should I enter to give an initial value for the parameter.  I gave some numbers. It does run. Also, after I hit go, there is no plot. Can anyone help? Thanks a lot!

stevedenham

That's a logit there, so you can fit logit(Y) = a' + bx, and the values to insert for A will be exp(a') and for B, simply b.

Good luck.

Steve Denham