pdf("trouthead.pdf")

thead1 <- read.fwf("C:\\data\\trouthead.dat", width=c(8,8,8,8),
col.names=c("gender", "lake", "head", "body"))

fgender <- factor(thead1$gender,levels=1:2)
levels(fgender) = c("M","F")

flake <- factor(thead1$lake,levels=1:2)
levels(flake) = c("KL", "WL")

thead <- data.frame(fgender, flake, head=thead1$head, body=thead1$body, lake=thead1$lake)

theadf <- subset(thead,fgender=="F")

attach(theadf)

lhead = log10(head)

lbody = log10(body)

lbodybar <- rep(mean(lbody),length(lbody))

lbodydev <- lbody-lbodybar

mean(lhead)

sd(lhead)

mean(lbody)

sd(lbody)

kl=-(lake-2)    ## Kl=1 if Lake=1, 0 if Lake=2

wl=lake-1       ## wl=1 if Lake=2, 0 if Lake=1



trout.acov <- lm(lhead ~ kl + wl + lbodydev -1)     ## -1 means no intercept

summary(trout.acov)

dev.off()