topic Re: How to constrain asymptotes in 4PL Hill curve fit? in Discussions

How to constrain asymptotes in 4PL Hill curve fit?

CriticalIguana6 — Mon, 28 Apr 2025 19:26:35 GMT

New user of JMP, running JMP18 and know how to perform basic 4PL fitting. 4PL Fitting is extremely important in many biological assays and we often need to set values of upper or lower asymptote when fitting incomplete IC50 curves with 4PL analysis.

Using the 4P Hill fitting equation, is there a way to constrain the asymptotes within graph builder

without having to create a custom model?

Thank you.

Re: How to constrain asymptotes in 4PL Hill curve fit?

Byron_JMP — Mon, 28 Apr 2025 20:43:26 GMT

The easy answer is that Graph Builder isn't a curve fitting application, only a graphing application.

The second easy answer is that they should transform their data to a 0 to 1 scale. that way the upper and lower asymptotes are constrained by default.

The third, not quite as easy answer: Simple curve fitting with the hill model is in Fit Curve, and in Non-linear you can control the parameters.

Re: How to constrain asymptotes in 4PL Hill curve fit?

Mark_Bailey — Tue, 29 Apr 2025 14:25:51 GMT

You might need to use the Analyze > Specialized Modeling > Nonlinear platform. It has a model library that includes the Hill equation. You could edit the model formula and replace the parameter for the asymptote with a constant. See this chapter in the JMP documentation for details.