Creating a DataFrame

You are examining the students' grade data, which is available in your environment as grades_array. Each array element is a string of 4 letters for a student's mathematics, history, science, and drama grades.

In the last chapter, you wrote a function called get_gradenumber(grades, n) to select the nth grade from the grade string grade. The function's first argument is the grade string, and the second argument is the number n from 1-4. The grades in each string are for mathematics, history, science, and drama, respectively.

The DataFrames package has been imported for you with the using keyword.