How can I make a legend in ggplot2 with one point entry and one line entry?

Question

I am making a graph in ggplot2 consisting of a set of datapoints plotted as points, with the lines predicted by a fitted model overlaid. The general idea of the graph looks

Answer 1

I think this is close to what you want:

ggplot(ex_data, aes(x=xvals, group=names)) + 
  geom_point(aes(y=yvals, shape='data', linetype='data')) + 
  geom_line(aes(y=pvals, shape='fitted', linetype='fitted')) + 
  scale_shape_manual('', values=c(19, NA)) + 
  scale_linetype_manual('', values=c(0, 1))

The idea is that you specify two aesthetics (linetype and shape) for both lines and points, even though it makes no sense, say, for a point to have a linetype aesthetic. Then you manually map these "nonsense" aesthetics to "null" values (NA and 0 in this case), using a manual scale.