Given the above table, I want to generate a line chart that displays, for each Student by Program Day, the % change in the Student's weight from their first recorded Weight value; ie (current weight - first weight) / first weight. Note that I say first Weight instead of weight on Day 1 because the first weight doesn't have to coincide with Day 1 but it will always be recorded on the lowest Program Day value for that student.
How do I reference the first weight value in my % change expression?
