Further update - I've tried the Custom SQL queries report plugin, which does allow embedding javascript in the description, but it seems that it only supports site-wide reports, and the report I'm trying to make is course bound (I filter the results using '%%COURSEID%%' which isn't supported in that plugin).
If there is any other free plugin out there with which I may achieve this ('this' referring to plotting a line/scatter graph from data gathered with a custom SQL query regardless if that means using javascript, or a built in plotting feature), I'd love to hear about it.
Also, bump...
