ggplot2 - extracting values of smooth

Suppose that I'm working on Hadley's diamond dataset and I want to
review the relationship between price, colour and carat.

I might run the following:

library(ggplot2)

#plot scatter and add some hex binning
     q<-qplot(carat,price,data=diamonds, geom=c("hex"),
             main="Variability of Diamond Prices by Carat and Colour")

#facet to get one scatter for each colour, plus overlay a black
coloured loess smoothed line showing the trends in the data

    q +
facet_wrap(~color,ncol=2)+geom_smooth(aes(group=1),colour=I("black"))

Nice picture, but how do I extract the values of the smoothed line?

Many thanks, dM/