Cwomen1 <- read.table("c:/temp/BFox.txt",header=F,skip=1)
names(Cwomen1)  <- c("year","participation","tfr","menWages","womenWages","debt","parttime") 

Cwomen1$tfr  <- Cwomen1$tfr*(Cwomen1$year != 1973) +1931*(Cwomen1$year == 1973)

Cwomen$time <- Cwomen$year - 1945

# use the leaps package to perform model selection

library(leaps)

ModFit1.SubFit <- regsubsets(participation ~ tfr +menWages +womenWages +debt 
                            +parttime +year, data=Cwomen1, nbest=3)

# use the car package to make interesting plots of the results 
# from the regsubsets function

library(car)


subsets(ModFit1.SubFit,statistic="bic")

subsets(ModFit1.SubFit,statistic="adjr2")

subsets(ModFit1.SubFit,statistic="bic",min.size=2)




# use the MASS package and the stepAIC function to perform 
# backward selection using an AIC criterion


CWMod1 <- lm(participation ~ tfr +menWages +womenWages +debt +parttime +time, data=Cwomen1)

library(MASS)

stepAIC(CWMod1,k=2)