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Student Support Forum: 'NonlinearFit to 4 Parameter Logistic' topicStudent Support Forum > General > "NonlinearFit to 4 Parameter Logistic"

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John
11/26/04 00:04am

I am trying to fit a 4PL model using NonlinearFit:

NonlinearRegress[points,p2+(p1-p2\)/((1+/p3))^p4, x, {{p1,.12,0,3}, {p2, 1,.5,3}, {p3,3000, 2500, 4000}, {p4,.8,.5,1.5}}]

I am getting the following error:

FindFit::dupv: "Duplicate variable p2 found in FindFit General::dupv"

Any suggestions for getting around this problem?

Thank You,

John

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