Dear all,

I am trying to do weighted regression using lm function in R. However, I have a question why the results from


1)      lm(formula = Y~aX, weight = w)

2)      lm(formula = wY~waX)

are different. Aren't they supposed to have the exactly same result?


Below are the R code to see difference in regression results

MatY <- c(0.15,0.42,0.31,0.22)
MatX <- rbind(c(1,0,0),c(0,1,0),c(1,0,0),c(0,0,1))
Data <- data.frame(cbind(MatY,MatX))
colnames(Data)[2]<-paste("IndSub1")
colnames(Data)[3]<-paste("IndSub2")
colnames(Data)[4]<-paste("IndSub3")
Weight <- c(0.1,0.4,0.3,0.2)

Result<- lm(formula = MatY~IndSub1+IndSub2+IndSub3-1, data = Data, weight = Weight)
summary(Result)

Data2 <- Data*Weight

Result2<- lm(formula = MatY~IndSub1+IndSub2+IndSub3-1, data = Data2)
summary(Result2)







Best Regards,
Suphajak Ngamlak
Asset Management (Hedge Fund)
Phatra Securities Public Company Limited
Tel: (66)2-305-9179
Email: suphajak@phatrasecurities.com


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