h<-seq(from=0.1,to=0.5,by=0.01)
k1<-matrix(NA,nrow = length(testxy$x),ncol =length(trainxy$x))
kh<-function(x0,x,h){
  for(i in 1:length(testxy$x)){
    for(j in 1:length(trainxy$x)){
      m<-(x0[i]-trainxy$x[j])/h
      k1[i,j]<-k(m)/h
  }
    }
  return(k1)
}
for(i in 1:length(h)) {
  K<-kh(testxy$x,trainxy$x,h[i])
}
a<-apply(K,MARGIN = 1,FUN = sum)
y1<-matrix(trainxy$y,nrow = 99,ncol = 1)
b<-K%*%y1
y2<-b/a
为什么只用了最后一个i的值