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Plots of data are useful to investigate relationships between variables. To examine, for example, the relationship between the performance of students in Programming in Semesters 1 and 2, we could write

plot(prog1, prog2, xlab = "Programming Semester 1", ylab = "Programming Semester 2")

to obtain Fig. 3.14.

Figure 3.14 A Scatter Plot

When more than two variables are involved, R provides a facility for producing scatter plots of all possible pairs.

To do this, first create a data frame of all the variables that you want to compare.

courses <- results[2:5]

This creates a data frame containing the second to the fifth variables in , that is, and . Writing

pairs(courses)

or equivalently

pairs(results[2:5])

will generate Fig. 3.15, which, as you can see, gives scatter plots for all possible pairs.

Figure 3.15 Use of the Function