LagrangePolynomial?lt;-?function(x,y)?{ len?=?length(x) if(len?!=?length(y))

stop( "length?not?equal!") if(len?lt;?2)

stop("dim?size?must?more?than?1") #pretreat?data?abd?alloc? memery xx?lt;-?paste("(","a?-",x,")") m?lt;-?c(rep(0,len)) #combin?express for(i?in? 1：len)?{

td?lt;-?1

tm?lt;-?"1"

for(j?in?1 ：len)?{ if(i?!=?j)?{

td?lt;-?td*(x[i]?-?x[j])

tm?lt;-?paste(tm, "*", xx[j]) }

}

tm?lt;-?paste(tm, "/", td)

m[i]lt;-tm?#m[i]?lt;-?parse(text=tm) } #combin?the?exrpession m?lt;-?paste(m ,"*",y) r?lt;-?paste(m,collapse=" ") #combin?the?function fbody?lt;-?paste("{?return(",r,")}") f?lt;-?function(a)?{} #fill?the?function's?body body(f)?lt;-?parse(text=fbody) return(f)

}

This is the Lagrangian polynomial interpolation algorithm? Please refer to it