The Art of R Programming

Extended Example: Regression Analysis of Exam Grades

For our next example, we’ll walk through a brief statistical regression analysis. There isn’t much actual programming in this example, but it illustrates how some of the data types we just discussed are used, including R’s S3 objects. Also, it will serve as the basis for several of our programming examples in subsequent chapters.

I have a file, ExamsQuiz.txt, containing grades from a class I taught. Here are its first few lines:

2    3.3   4
3.3  2     3.7
4    4.3   4
2.3  0     3.3
...

The numbers correspond to letter grades on a four-point scale; 3.3 is a B+, for instance. Each line contains the data for one student, consisting of the midterm examination grade, final examination grade, and average quiz grade. ...