## ----------------------------------------------------------------------------
##   R scripts for Haerdle/Mueller/Sperlich/Werwatz: "Nonparametric and
##   Semiparametric Modelling", Springer Series in Statistics, 2004
## ----------------------------------------------------------------------------
##   Script      SPMknnregression
## ----------------------------------------------------------------------------
##   Description computes the regression of food on net-income 
##               for the UK 1976 expenditure data.
## ----------------------------------------------------------------------------
##   Author      Marlene Mueller, 2008/12/19
## ----------------------------------------------------------------------------

x <- read.csv2("D:\\fes76.txt", dec=".")
x <- x[,c("NIC","FOO")]
x <- x[order(x$NIC),]

plot(x,col="lightblue",pch=20,main="Engel Curve: k-NN regression")

library(kknn)

n.grid <- 100
NIC.grid <- seq(min(x$NIC),max(x$NIC),length=n.grid)
test.grid <- data.frame(NIC=NIC.grid,FOO=rep(0,n.grid))

mh <- kknn(FOO ~ NIC, x, test.grid, k=50, kernel="rectangular")
##mh <- kknn(FOO ~ NIC, x, test.grid, k=50, kernel="biweight")
lines(NIC.grid,fitted(mh))