Application and Uses of Four-Parameter Estimates of Nonlinear Growth Analysis

Abstract

The partial derivatives of the four parameters estimates; Chapman-Richards, von Bertalanffy, Weibull and the Richard’s nonlinear growth models are presented and compared. The application of these partial derivatives in estimating the model parameters is illustrated. The parameters are estimated using the Marquardt iterative method of nonlinear regression relating top height to age of Palm tree from the Rhison palm Estate, Rivers State Nigeria. Formulas that provide good initial values of the parameters are specified. Clear definitions of the parameters of the nonlinear models in the context of the system being modeled are found to be critically important in the process of parameter estimation. The Richard’s, and the Weibull models have produced a slightly smaller residual standard error (0.13 m) compared to the von Bertalanffy and the Chapman- Richards models (0.14 m). All the models in Table 8 appear to predict reasonable estimates over the entire range of age.