#Two way Analysis of variance for balanced designs (equal group size)
install.packages("car")
library(car)


my_data <- read.table("twaov.txt", header=T)
attach(my_data)


#####Two-way ANOVA without interaction#####
#Type does not matter in a balanced design#

model2 <- lm(activity ~ predator_density + timing, data = my_data)
Anova(model2,type="II")



####Check model assumptions####

#Assumption 1: Normal distribution of the model residuals
plot(model2,2)

#Assumption 2: Homogeneity of variance of the groups
plot(model2,1)


#Post-hoc test: In case of a non-significant interaction effect, we conduct tests for each main effect seperately
install.packages("lsmeans")
library("lsmeans")


lsmeans(model2,
        pairwise ~ predator_density)

lsmeans(model2,
        pairwise ~ timing)   



#####data visualization#####
install.packages("ggplot2")
library(ggplot2)

ggplot(aes(y = activity, x = timing, fill = predator_density), data = my_data) + geom_boxplot() + theme_bw()