topic Re: Logistic 5P (Richard Function) in Discussions

Logistic 5P (Richard Function)

RO1 — Wed, 29 Jan 2025 21:21:43 GMT

Hi, can anyone provide information on the meaning of the parameters of the Logistic 5P Richard function especially theta3? (jmp8)

Re: Logistic 5P (Richard Function)

txnelson — Wed, 29 Jan 2025 21:27:41 GMT

Welcome to the Community.

Wow.....JMP8. I have not seen any responders on the Community Forum that have access to JMP8. Maybe a JMP folk.

Have you looked used the ? tool and clicked on the report that has the statistic you are asking about. It should take you to information on it. Or go to Help and search on the platform the report was generated from. There should be a section Statistical Details.

Re: Logistic 5P (Richard Function)

RO1 — Wed, 29 Jan 2025 22:38:37 GMT

Thank you Jim. I had not seen exactly this guide to nonlinear modeling references, and it is helpful. However, there is no reference for the Logistic 5P (Richard Function). I have found several models in the literature, but none are exactly like what is given in JMP. If someone has a reference for this model, theta1 + [(theta2-theta1)/(1+Exp(theta3+theta4*X))^theta5)], it would be appreciated. The one that is troubling me is theta3.

Thank you

Re: Logistic 5P (Richard Function)

txnelson — Thu, 30 Jan 2025 02:39:12 GMT

With luck, a Community member will be able to provide you with the information.

Re: Logistic 5P (Richard Function)

Victor_G — Thu, 30 Jan 2025 08:48:43 GMT

Hi @RO1,

You can find an explanation about the terms of the Logistic 5P function here : Statistical Details for Fit Curve Models

The letters may be different, but the equation is the same. When expanding the expression from JMP Help, theta3 would be related to the term a.b in the equation, so it would be related to growth rate and location.

You can also find explanations about the terms in this equation here : Brendan Bioanalytics : 5PL Curve Fitting
Help Online - Origin Help - Logistic5

Hope this answer may help you,

Re: Logistic 5P (Richard Function)

RO1 — Thu, 30 Jan 2025 12:58:45 GMT

Thank you Victor

Re: Logistic 5P (Richard Function)

RO1 — Thu, 30 Jan 2025 13:41:42 GMT

One thing though - I assumed that theta4 was related to growth rate.