script for video walkthrough on using R/RStudio for 3-way ANOVA

L3_stats_homework_5_2016.R

## youtube video: https://youtu.be/AJDo9gpkEcg
library("readr")
library("ggplot2")

## read.csv() <- from base R.  DON'T USE!
hw5 <- read_csv("homework_5.csv") # from readr

hw5$A <- factor(hw5$A)
hw5$B <- factor(hw5$B)
hw5$C <- factor(hw5$C)

## aov(Y ~ A + B + C + A:B + A:C + B:C + A:B:C, hw5)
my_anova <- aov(Y ~ A * B * C, hw5)

summary(my_anova)

## base R   interaction.plot()
## ggplot2  geom_line() geom_point()

## dplyr: filter
## logical expression:
##   an expression that returns 
##     TRUE or FALSE
hw5_c1 <- subset(hw5, C == "C1")
hw5_c2 <- subset(hw5, C == "C2")

par(mfrow = c(1, 2))
## interaction.plot(hw5_c1$A,
##                 hw5_c1$B,
##                 hw5_c1$Y)
with(hw5_c1, interaction.plot(A, B, Y, legend = TRUE))

## interaction.plot(hw5_c2$A,
##                 hw5_c2$B,
##                 hw5_c2$Y)
with(hw5_c2, interaction.plot(A, B, Y, legend = TRUE))

cell_means <- aggregate(Y ~ A + B + C,
                        hw5, mean)

ggplot(cell_means, 
       aes(A, Y, linetype = B, shape = B, group = B)) +
  geom_line() + geom_point(size = 3) +
  facet_wrap(~C)