##------------------------------------------------------------------------## ## Script for web appendix on nonlinear regression ## ## An R and S-PLUS Companion to Applied Regression ## ## John Fox ## ## Sage Publications, 2002 ## ##------------------------------------------------------------------------## # preliminaries options(width=65) options(digits=5) ## Nonlinear Regression par(mfrow=c(1,2)) library(car) data(US.pop) attach(US.pop) plot(year, population, main='(a)') library(nls) time <- 0:20 pop.mod <- nls(population ~ beta1/(1 + exp(beta2 + beta3*time)), start=list(beta1=350, beta2=4.5, beta3=-0.3), trace=T) summary(pop.mod) lines(year, fitted.values(pop.mod), lwd=2) plot(year, residuals(pop.mod), type='b', main='(b)') abline(h=0, lty=2)