Time for action – calculating statistics with the use of a subtransformations

Suppose that you are responsible to collect the results of an annual examination that is being taken in a language school. The examination evaluates English, Mathematics, Science, History, and Geography skills. Every professor gives the exam paper to the students, the students take the examination, the professors grade the examinations on a scale of 0-100 for each skill, and write the results in a text file, like the following:

student_code;name;english;mathematics;science;history_and_geo
80711-85;William Miller;81;83;80;90
20362-34;Jennifer Martin;87;76;70;80
75283-17;Margaret Wilson;99;94;90;80
83714-28;Helen Thomas;89;97;80;80
61666-55;Maria Thomas;88;77;70;80
00647-35;David Collins;88;95;90;90

All the files follow that pattern.

In this section and in the sections to come, you will use these files to run different kinds of transformations. Before starting, get the sample files from the book site.

Now, let...