Performing a two-way ANOVA
A two-way ANOVA can be viewed as the extension of a one-way ANOVA, for the analysis covers more than two categorical variables rather than one. In this recipe, we will discuss how to conduct a two-way ANOVA in R.
Getting ready
Ensure that mtcars has already been loaded into a data frame within an R session. Since the twoway.test, TukeyHSD and interaction.plot functions are originated from the stats package, make sure the library, stats, is loaded.
How to do it...
Perform the following steps:
- First we plot the two boxplots of factor gears in regard to mpg, with the plot separated from the transmission type:
> par(mfrow=c(1,2)) > boxplot(mtcars$mpg~mtcars$gear,subset=(mtcars$am==0),xlab='gear', ylab = "mpg",main='automatic') ...
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