An gganimate and DW-NOMINATE scores
In a previous life, I studied how the U.S. Congress made laws. One question I was especially interested in was how the ideological composition of Congress changed over time. This is kind of a nice question to be interested in because Congress has existed in a current form for a few hundred years. Combined with the fact that we can estimate ideology using roll call votes, we have lots of data! There are TONS of books about how legislative ideology has changed over time. However, side stepping all that, we can see the changes in member ideology by plotting DW-NOMINATE scores over time. More specifically for this post, we can animate changes in DW-NOMINATE scores over time using gganimate.