PTSD2<-PTSD
PTSD2$G<-as.numeric(unclass(PTSD$GROUP))
PTSD2$D1<-as.numeric(PTSD2$G==1)
PTSD2$D2<-as.numeric(PTSD2$G==2)
PTSD2$D3<-as.numeric(PTSD2$G==3)
PTSD2$D4<-as.numeric(PTSD2$G==4)

summary(aov(PTSD~GROUP,data=PTSD2))


library(gplots)
plotmeans(PTSD~GROUP,data=PTSD2)

summary(lm(PTSD~GROUP,data=PTSD2))

summary(lm(PTSD~D2+D3+D4,data=PTSD2))

summary(lm(PTSD~D1+D2+D3+D4,data=PTSD2))

summary(lm(PTSD~-1+D1+D2+D3+D4,data=PTSD2))

#######################################################

my.url<-'http://www.math.mcgill.ca//dstephens//204//Data//muscle1.txt'

muscle <- read.table(url(my.url),header=TRUE)

str(muscle)

plot(muscle$mass,muscle$heat,pch=18)
plot(muscle$work,muscle$heat,pch=18)

summary(aov(heat~as.factor(work),data=muscle))

summary(lm(heat~as.factor(work),data=muscle))
plotmeans(heat~as.factor(work),data=muscle)

m1<-lm(heat~work,data=muscle)
summary(m1)
plot(muscle$work,muscle$heat,pch=18)
abline(m1$coef,col="red",lwd=2)