please help me and correct why this program give me error
bcos I want to apply the condition follow the attached below
# program (R) used estimate beta of robust ridge (weighted stacklose)
rm(list=ls())
library(MASS)
library(mvoutlier)
library(robustbase)
library(car)
library(quantreg)
n<-21
p<-3
data<-read.csv('C:/Users/Kafi/Documents/stacklose.csv',header=TRUE)
cell<-data
y<-as.matrix(cell[,1])
x1<-cell[,2]
x2<-cell[,3]
x3<-cell[,4]
stack<- as.matrix(data.frame(y,x1,x2,x3))
stack
d <- lm(y ~ x1+x2+x3)$residuals
d1<-lm(y ~ x1+x2+x3)$fit
d2<-abs(d)
k<-4.685
w<-NULL
for(i in 1:n){
if(d2<=k){w[i]=d{1-(d/k)^2}^2} else{w[i]=0}}
w
Kafi Dano Pati
Ph.D candidate ( mathematics/statistics)
Department of mathematical Science/ faculty of Science
University Technology Malaysia
81310 UTM, Johor Bahru, Johor, Malaysia
IC. NO. 201202F10234
Matric No. PS113113
HP. No. 00601117517559
E-mail: kafi_dano at yahoo.com
supervisor- Assoc. Prof. Robiah Binti Adnan