Two ways to complete the FilterAndSummarize task used in Skill Tree documentation. See http://skill-tree.org/design/skilled-performance
The file create_data.php creates a data set to work on. It created the file messages.csv.no_errors. I messed up a few records to create messages.csv.
filter_summarize.php is a solution that a student might create, at the end of an intro programming course.
filter_summarize_with_class.php is a solution that an expert might create. The rest of the files in the repo support this solution.