Gompertz Function

Modelling Constrained Growth

Brandon Bartell
Nerd

What is the Gompertz function?

  • The Gompertz function is a simple mathematical model for constrained growth as a function of time.

  • It was named after Benjamin Gompertz, who was a british mathematician and actuary.

  • It takes the form: \[ y(t)=a e^{-b e^{-c t}} \]

  • a, b, and c are the three parameters that describe the shape as the function varies with time, t

Why use it?

  • The Gompertz function is practical for its simplicity and power
  • With 3 simple parameters, you can easily model
    • Population growth with finite resources
    • Tumor growth in a confined space
    • Product/technology share uptake to peak share

What does each parameter do?

  • Here are some examples showing how the curve moves with each parameter, leaving the other parameters fixed.

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Playing with it yourself!

  • In order to understand what each parameter in the Gompertz function does, it is useful to play with each parameter and visually see it's effect on the shape of the curve.

  • My shiny app lets the user change the three parameters and the plotting range interactively.

  • Try it for yourself!