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$log2wages <- log2(SLID1$wages)


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

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

 # automatically generates several useful plots
par(mfrow=c(2,2)) 
plot(SLID1.lm2)
par(mfrow=c(1,1)) 



 # ---------------------------------------------------------------------
 # Create the partial residual plots                                    
 # ---------------------------------------------------------------------

library(car)

cr.plots(SLID1.lm2,variable="age")

cr.plots(SLID1.lm2,variable="yearsed")


 # ------- here the two plots are in the same figure -------------------

par(mfrow=c(1,2)) 
cr.plots(SLID1.lm2,variable="age")
cr.plots(SLID1.lm2,variable="yearsed")
par(mfrow=c(1,1))