Nonlinear Regression
EXAMPLE: Population Growth - Predator Prey models
(page 180 RWG)
DeBlois and Leggett (1991) set up expermental aquaria to study
dynamics of simple predator/prey systems. They found that the rates of
predation by amphipods (a small crustecean) were nonlinearly related to
the initial density of their prey, capelin eggs.
We will explore nonlinear regression to fit models to the
predator prey data in class and in lab this week.
Variables in the data set
- case/experiment number
- Initial Egg density (eggs/cm^3)
- Capelin Eggs eaten/amphipod (response variable)
HANDOUTS:
SAS CODE for fitting the GOMBERTZ model and output.
Fitted GOMBERTZ model and data
General Procedure for Fitting Nonlinear Models
- Get initial estimates of parameters by approximate linear regression model
- Fit nonlinear regression using guestimates