Chapter 14 Nonlinear Growth Curves

This chapter introduces the concept of nonlinear change. In this chapter we will cover the following topics:

1. Review of Linear Growth
   • Theory of Linear Growth
   • Characteristics of Linear Growth
   • No Growth Model
     • Equations
     • Code (NLME/LME)
   • Random Intercept Model
     • Equations
     • Code (NLME/LME)
   • Linear Growth Model
     • Equations
     • Code (NLME/LME)
   • Quadratic Growth Model
     • Equations
     • Code (NLME/LME)
2. Introducing Nonlinear Growth
   • Types of Nonlinear Models
     • Type I: Nonlinear in Time
     • Type II: Nonlinear in Parameters
     • Type III: Nonlinear in Random Coefficients
   • Flexibility of Nonlinear Growth
   • Utility of Nonlinear Growth
   • Some Nonlinear Growth Models
   • Need for Nonlinear Models
3. Example Data (Ram and Grimm, 2007)
   • Read in Cortisol Data
   • Reshaping Data
   • Descriptives
   • Density Plots
   • Individual-level Trajectories
4. Linear Growth (Cortisol)
   • Equation
   • Fit Model _ Plots
   • Interpretation
5. Quadratic Growth (Cortisol)
   • Equation
   • Fit Model _ Plots
   • Interpretation
6. Latent Basis (Cortisol)
   • Equation
   • Fit Model _ Plots
   • Interpretation
7. Exponential Growth (Cortisol)
   • Equation
   • Fit Model _ Plots
   • Interpretation
8. Multiphase Growth (Cortisol)
   • Equation
   • Fit Model _ Plots
   • Interpretation