SLID1 <- read.table("c:/temp/SLID-Ontario.txt",sep = "\t",header=F,skip=1)
names(SLID1)  <- c("age","sex","wages","yearsed")

SLID1$male <- as.numeric(SLID1$sex == "Male")

SLID1$age2 <- SLID1$age^2
SLID1$yearsed2  <-  SLID1$yearsed^2

SLID1$log2wages <- log2(SLID1$wages)


 # --------- regression with the log base 2 data -----------------

SLID1.lm2 <- lm(log2wages ~ male +age +age2 +yearsed2, data=SLID1)

summary(SLID1.lm2)

 # the vcov function extracts the covariance matrix of the coefficient estimates

vcov(SLID1.lm2)