Generalised logistic function

The generalised logistic (or Richard's) curve is a widely used and flexible function for growth modelling.

Y = A + ( C / (1 + T e)^(-B(x - M)^1/T) )

where Y=weight, height, size etc; X = time.

It has five parameters:

A

the lower asymptote;

C

the upper asymptote;

M

the time of maximum growth;

B

the growth rate;

T

near which asymptote maximum growth occurs.