Modeling and Multivariate Methods - SAS

Chapter 9
Performing Nonlinear Regression
Using the Nonlinear Platform
In many situations, especially in the physical and biological sciences, well-known nonlinear equations
describe the relationship between variables. For example, bioassay experiments are conducted by
pharmacology researchers to understand how the strength of the response to a drug changes as a function of
drug concentration. The Logistic family of curves often accurately describes how the response strength is
related to drug concentration. Another example is exponential growth curves, which can predict the size of a
population over time.
The Nonlinear platform makes it easy to fit common nonlinear relationships. The Fit Curve personality of
the Nonlinear platform has a library of built-in models. Fit Curve also enables the user to compare different
groups or subjects using a variety of analytical and graphical techniques.
The Nonlinear platform also has a general nonlinear modeling framework for fitting user-defined nonlinear
models and loss functions not found in the library of built in models.
Figure 9.1 Example of Nonlinear Fit