We have used a new geom here, geom_smooth. The geom_smooth function creates a smoothed conditional mean. Basically, we’re drawing some line as a result of a function based on this input data. Notice that there are two parameters that I set: method and se. The method parameter tells the function which method to use. There are five methods available, including using a Generalized Additive Model (gam), Locally Weighted Scatterplot Smoothing (loess), and three varieties of Linear Models (lm, glm, and rlm). The se parameter controls whether we want to see the standard error bar.
I don’t cover all of the mapping options and all of the geoms, but I think it’s enough to get a grip on the concept.