pdf("swamp.pdf")

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

fsize <- factor(swamp$size, levels=1:3)

levels(fsize) <- c("Small", "Medium", "Large")

swamp1 <- data.frame(watlev=(swamp$watlev), swampid=factor(swamp$swampid), fsize)

attach(swamp1)

tapply(watlev, fsize, mean)

tapply(watlev, swampid, mean)

tapply(watlev, swampid, sd)

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

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

summary(swamp.aov1)

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

# This provides appropriate F-test for fsize

summary(swamp.aov2)

dev.off()