This variation of the happinessradar activity gets the average happiness over a timeline. It worked well for a release retrospective. The main difference for it and the typical happiness radar is that the column titles are time based, instead of being area specific.
Below is a photo from a happiness radar used on a large group retrospective where the context included a long timeline for a event (from 9 months ago since that event at SP; last month; the last 3 days—from the day the event started until now).
On building the happiness radar on the photo above, first I drew the timeline on the top of the canvas. Then I drew the faces and asked people to get their marks on each table cell. The happiness radar post has a step by step on running the activity.