#LM 03 ANCOVA SINGLE FACTOR
#KNNL TABLE 22.1
setwd("c:/DATA/Models")
K=read.table("CH22TA01.txt",header=TRUE)
K
attach(K)
T=factor(treatment)



plot(X,Y,pch=20)
points(X[treatment==1],Y[treatment==1],pch=20,col="red")
points(X[treatment==2],Y[treatment==2],pch=20,col="blue")
points(X[treatment==3],Y[treatment==3],pch=20,col="green")

library(nlme)
LM=lmList(Y~X|T,data=K)
plot(fitted(LM))

# GLM TEST OF TREATMENT EFFECT (INTERCEPT):
FM=lm(Y~X+T) #FULL MODEL
summary(FM)
anova(FM)

RM=lm(Y~X)  #REDUCED MODEL
summary(RM)
anova(RM)

n=length(Y)  #number of objects in dataset
c=4 #number of estimated parameters (3 classes of T + 1 for X)

anova(FM,RM)

#GLM TEST OF PARALLEL SLOPE:

FMs=lm(Y~X*T)
summary(FMs)
anova(FMs)

RMs=lm(Y~X+T) #same model as FM above but now used as the reduced model
summary(RMs)
anova(RMs)

anova(FMs,RMs)