I'm endeavoring to add a legend after creating a ggplot showing regression lines. I used the following code, which creates the plot, but doesn't seem to give me any option to add a legend. (It appears geom_abline automatically sets show.legend to FALSE if you specify a particular slope or intercept.) Can someone advise the best way to do this? Appreciate your advice.
ggplot(dat, aes(y=PCTGRAD,x=SAT))+geom_point(cex=0.5)+geom_abline(intercept=private.intercept,slope=slope,col="red", show.legend=TRUE)+geom_abline(intercept=public.intercept, slope=slope, col="blue", show.legend=TRUE)