Repeated measures ANOVA is a common task for the data analyst.
There are (at least) two ways of performing “repeated measures ANOVA” using R but none is really trivial, and each way has it’s own complication/pitfalls (explanation/solution to which I was usually able to find through searching in the R-help mailing list).
So for future reference, I am starting this page to document links I find to tutorials, explanations (and troubleshooting) of “repeated measure ANOVA” done with R
- A basic tutorial about ANOVA with R (only the last bit holds some example of repeated measures) on personality-project
- A thorough tutorial on motor control lab
- A thorough tutorial on UCLA seminar page
- Another good tutorial by
Jonathan Baron and Yuelin Li (on “Notes on the use of R for psychology experiments and questionnaires”
Unbalanced design doesn’t work when doing repeated measures ANOVA with aov, it just doesn’t. This situation occurs if there are missing values in the data or that the data is not from a fully balanced design. The way this will show up in your output is that you will see the between subject section showing withing subject variables.
A solution for this might be to use the Anova function from library car with parameter type=”III”. But before doing that, first make sure you understand the difference between SS type I, II and III. Here is a good tutorial for helping you out with that.
By the way, these links are also useful in case you want to do a simple two way ANOVA for unbalanced design
I will “later” add R-help mailing list discussions that I found helpful on the subject.
If you come across good resources, please let me know about them in the comments.