Programming with Perl

The best way to learn how to program is to do something useful, so this introduction to Perl is built around a common scientific task: data analysis.

Our real goal isn't to teach you Perl, but to teach you the basic concepts that all programming depends on. We use Perl in our lessons because:

1. we have to use something for examples;
2. it's free, well-documented, and runs almost everywhere;
3. it has a large (and growing) user base among scientists; and
4. experience shows that it's easier for novices to pick up than most other languages.

But the two most important things are to use whatever language your colleagues are using, so that you can share you work with them easily, and to use that language well.

We are studying inflammation in patients who have been given a new treatment for arthritis, and need to analyze the first dozen data sets. The data sets are stored in comma-separated values (CSV) format: each row holds information for a single patient, and the columns represent successive days. The first few rows of our first file look like this:

0,0,1,3,1,2,4,7,8,3,3,3,10,5,7,4,7,7,12,18,6,13,11,11,7,7,4,6,8,8,4,4,5,7,3,4,2,3,0,0
0,1,2,1,2,1,3,2,2,6,10,11,5,9,4,4,7,16,8,6,18,4,12,5,12,7,11,5,11,3,3,5,4,4,5,5,1,1,0,1
0,1,1,3,3,2,6,2,5,9,5,7,4,5,4,15,5,11,9,10,19,14,12,17,7,12,11,7,4,2,10,5,4,2,2,3,2,2,1,1
0,0,2,0,4,2,2,1,6,7,10,7,9,13,8,8,15,10,10,7,17,4,4,7,6,15,6,4,9,11,3,5,6,3,3,4,2,3,2,1
0,1,1,3,3,1,3,5,2,4,4,7,6,5,3,10,8,10,6,17,9,14,9,7,13,9,12,6,7,7,9,6,3,2,2,4,2,0,1,1

We want to:

• load that data into memory,
• calculate the average inflammation per day across all patients, and
• plot the result.

To do all that, we'll have to learn a little bit about programming.

Topics

1. Analyzing Patient Data
2. Creating Functions
3. Analyzing Multiple Data Sets
4. Making Choices
5. Defensive Programming
6. Command-Line Programs
7. Errors and Exceptions

Other Resources

• Motivation
• Reference
• Discussion
• Instructor's Guide