# highway data
version$language == "R"
if(is.null(version$language) == FALSE) data(highway)
a <- highway
a$logADT <- logb(a$ADT,2)
a$logTrks <- logb(a$Trks,2)
a$logLen <- logb(a$Len,2)
a$logSigs1 <- logb((a$Sigs*a$Len+1)/a$Len,2)
a$logRate <- logb(a$Rate,2)
# set the contrasts to the R default
options(contrasts=c(factor="contr.treatment",ordered="contr.poly"))
a$Hwy <- if(is.null(version$language) == FALSE) factor(a$Hwy,ordered=FALSE) else factor(a$Hwy)
attach(a)
names(a)
cols <- c(17,15,13,14,16,7,10,3,4,6,9,11)
m1 <- lm(logRate ~ logLen+logADT+logTrks+logSigs1+Slim+Shld+
                Lane+Acpt+Itg+Lwid+Hwy)
#write.table(a[,cols],"data/highway1.txt",row.names=FALSE,col.names=TRUE,
#   quote=TRUE)
if(is.null(version$language) == FALSE) {require (xtable); xtable(m1)} else m1

# step forward AIC
m0 <- lm(logRate ~logLen,data=a)
ansf1 <- step(m0,scope=list(lower=~logLen,
         upper=~logLen+logADT+logTrks+logSigs1+Slim+Shld+
                Lane+Acpt+Itg+Lwid+Hwy),
                direction="forward", data=a)