GROWTH CURVE MODELLING

Growth is a fundamental property of biological systems, occuring at the level of populations, individual animals and plants, as well as within organisms. Much research has been devoted to modelling growth processes, and there are many ways of doing this, including: mechanistic models, time series, stochastic differential equations etc.

Sometimes we simply wish to summarise growth observations in terms of a few parameters, perhaps in order to compare individuals or groups. Many growth phenomena in nature show an "S" shaped pattern, with initially slow growth speeding up before slowing down to approach a limit. These patterns can be modelled using several mathematical functions. Here we explore the generalised logistic and Gompertz curves.

Examples of applications of the technique include:

animal weights over time;
growth of human populations;
biomedical data;
development of organisms.