pdf("C:\\Rmisc\\graphs\\txtemp.pdf")

txtemp <- read.fwf("C:\\data\\texas1.txt",width=c(15,10,8,8,8),
col.names=c("county","jantemp","lat","long","elev"))

attach(txtemp)

txtemp.mod1 <- lm(jantemp~lat+long+elev)

summary(txtemp.mod1)
anova(txtemp.mod1)

txtemp.mod2 <- lm(jantemp~lat)

summary(txtemp.mod2)
anova(txtemp.mod2)

txtemp.mod3 <- lm(jantemp~lat+elev)

summary(txtemp.mod3)
anova(txtemp.mod3)

txtemp.mod4 <- lm(jantemp~lat*elev)

summary(txtemp.mod4)
anova(txtemp.mod4)

dev.off()