如何使用R语言编写牛顿插值公式对缺失值进行插值

LagrangePolynomial?<-?function(x,y)?{

len?=?length(x)

if(len?!=?length(y))

stop("length?not?equal!")

if(len?<?2)

stop("dim?size?must?more?than?1")

#pretreat?data?abd?alloc?memery

xx?<-?paste("(","a?-",x,")")

m?<-?c(rep(0,len))

#combin?express

for(i?in?1:len)?{

td?<-?1

tm?<-?"1"

for(j?in?1:len)?{

if(i?!=?j)?{

td?<-?td*(x[i]?-?x[j])

tm?<-?paste(tm,"*",xx[j])

}

}

tm?<-?paste(tm,"/",td)

m[i]<-tm?#m[i]?<-?parse(text=tm)

}

#combin?the?exrpession

m?<-?paste(m,"*",y)

r?<-?paste(m,collapse="+")

#combin?the?function

fbody?<-?paste("{?return(",r,")}")

f?<-?function(a)?{}

#fill?the?function's?body

body(f)?<-?parse(text=fbody)

return(f)

}

这是拉格朗日多项式插值算法?你参考下吧