I’d like to visualize the dynamics of two variables. Animation makes sense for this rather than a mere scatterplot with a dot for each point in time. Something in between a dot moving around and a scatter plot would help expose the dynamical relationship better. So it would basically be a scatter plot except with a “time_window” parameter.
I’ve seen stuff like this referred to as the “trails” offered by gapminder, but that’s overkill for what seems to me an obvious feature for any animated scatter.