water <- read.csv("http://www.stat.ufl.edu/~winner/sta4210/mydata/water_resource_dumvarreg.csv", header=TRUE) attach(water); names(water) water.mod1 <- lm(subsid ~ watertab) summary(water.mod1) anova(water.mod1) water.mod2 <- lm(subsid ~ watertab + truck + sugar) summary(water.mod2) anova(water.mod2) anova(water.mod1,water.mod2) water.mod3 <- lm(subsid ~ watertab + truck + sugar + I(watertab*truck) + I(watertab*sugar)) summary(water.mod3) anova(water.mod3) anova(water.mod2,water.mod3)