pdf("swamp.pdf")

swamp <- read.fwf("C:\\data\\swamp1.dat", width=c(8,8,8),
col.names=c("size", "swampid", "watlev"))

attach(swamp)

size <- factor(size, levels=1:3,labels=c("Small", "Medium", "Large"))
swampid <- factor(swampid)

tapply(watlev, size, mean)

tapply(watlev, swampid, mean)

tapply(watlev, swampid, sd)

swamp.aov1 <- aov(watlev ~ size + size/swampid)

# This provides ANOVA, not appropriate F-test for fsize

summary(swamp.aov1)

swamp.aov2 <- aov(watlev ~ size + Error(swampid))

# This provides appropriate F-test for fsize

summary(swamp.aov2)

dev.off()