########################################
#
#  Script: 6 April 2011 (preliminary)
#
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# Today:
#
#   ** Plotting 
#   ** Analysis of variance
#   ** Experimental design
#


# Let us create a new dataset (Ex 15.1, page 960)

ins <- data.frame( matrix( c(1,1,56, 1,2,48, 1,3,66, 1,4,62, 
  2,1,83, 2,2,78, 2,3,94, 2,4,93,
  3,1,80, 3,2,72, 3,3,83, 3,4,85), ncol=3, byrow=T))
names(ins) <- c("Ins","Plot","Seedlings")
ins$Plot   <- as.factor(ins$Plot)
ins$Ins    <- as.factor(ins$Ins)
ins        <- data.frame(ins)


attach(ins)


plot(Seedlings ~ Ins + Plot)
plot.design(Seedlings ~ Ins + Plot)
interaction.plot(Ins,Plot,Seedlings)
barplot( tapply(Seedlings, list(Ins,Plot),mean), beside=T )


m.ins <- aov(Seedlings ~ Ins + Plot)
summary(m.ins)


# Try fitting an interaction model here. What is the result?