ANOVA, Addditive& Interactive effects

ANOVA, RegTrees

x2=c(4,25,13,7,56,90,2,82)
x2=array(x2,c(2,4))
x2
tab=LTT.Kenya_Exe
tab
tab2=tab[1:464, 1:7]
tab2
names(tab2)
tab3=subset(tab,Site=="Bon" & "Nin"=="N0", select=c(Site,Var,Fert,Nin,Yield))
write.csv(tab, "LLT_BonN0")
write.csv(tab,"C:/Users/machariam/Desktop/LLT_BonN0")
#Analyis of variance
a=aov(tab$Yield~tab$Var)
a
summary(a)
par(mfrow=c(2,2))
plot(a) 
hist(tab2$Yield)
tab4=subset(tab,Yield<4,select=c(Site,Var,Fert,Nin,Yield))
a1=aov(tab4$Yield~tab4$Var)
par(mfrow=c(2,2))
plot(a1)
#Additive and interactive effects
names(tab)
tab5=subset(tab,Yield<4&Site=="Bon",select=c(Site,Var,Fert,Nin,Ssn,Yield))
View(tab5)
a2=aov(Yield~Var*Fert*Nin*Ssn,data=tab5)
summary(a2)
#Fert-fertility status, Nin-Nitrogen level, Ssn- Season
#signifcant difference in yield between variety irrespsctive of fertility
#status, N inputs and season
#Not significant=additive effect=N input has consistent effect on yield for all varieties, 
#irrespective of fertility status and season
#significant interactive effect=the yiled response of variety to N input is 
#different across seasons, irrespective of fertility status of soils
#Post-hoc pairwise comparison
require(stats)
TukeyHSD(a2)
#Principles of Non-parametric tests
#Try this if the sample is small and does not assume normal
#Creating barplots with error bars
tab6=aggregate(tab2$Yield, by=list(tab2$Var, tab2$Fert, tab2$Nin, tab2$Ssn),FUN="mean")
tab6