I recently hosted a competition at InClassKaggle.com. I have scores by team and day in which they were submitted. I want to present the results to students.

1) This one I can do. I want a graph of all the submissions of all groups and show the median by group.

2) This one I'm having trouble.  I want a graph of medians by day of submission. The idea is to show that as time went by the quality of submissions got better and better. But I can't get a median by day (only one for the entire table). I tried to add a reference line for the median value by cell but it doesn't change.