gistfile1.txt

# Have:
# A scatterplot with points grouped by binning a continuous variable.
(ggplot(mtcars, aes(wt, mpg, color=carb>2))
  +geom_point()
  +geom_smooth(aes(color=carb>2), method="lm"))

# Also have:
# A scatterplot with the smoothers grouped but points colored continuously
(ggplot(mtcars, aes(wt, mpg, color=carb))
  +geom_point()
  +geom_smooth(aes(lty=carb>2), method="lm"))

# Want: 
# Smoothers coded by one discrete color scale, points coded by a second continuous color scale
(ggplot(mtcars, aes(wt, mpg, color=carb))
  +geom_point()
  +geom_smooth(aes(color=carb>2), method="lm"))
# Error: Discrete value supplied to continuous scale