library(car)
attach(Prestige)
plot(income,prestige,xlab="Average Income",ylab="Prestige")
lines(lowess(income,prestige,f=0.5,iter=0),lwd=2)

mod.lo.inc<-loess(prestige~income,span=0.7,degree=1)
mod.lo.inc
inc.100<-seq(min(income),max(income),len=100)
pres<-predict(mod.lo.inc,data.frame(income=inc.100))
plot(income,prestige)
lines(inc.100,pres,lty=2,lwd=2)

library(splines)
lines(smooth.spline(income,prestige,df=3.85),lwd=2)
legend("bottomright",c("loess","smoothing splines"),lty=c(2,1),lwd=c(2,2))

library(mgcv)
mod.gam<-gam(prestige~s(income)+s(education))
mod.gam

inc<-seq(min(income),max(income),len=25)
ed<-seq(min(education),max(education),len=25)
newdata<-expand.grid(income=inc,education=ed)
fit.prestige<-matrix(predict(mod.gam,newdata),25,25)
persp(inc,ed,fit.prestige,theta=45,phi=30,ticktype="detailed",xlab="Income",ylab="Education",zlab="Prestige",expand=2/3,shade=0.5)

par(mfrow=c(1,2))
plot(mod.gam)