equation for lm graphics

I'm doing graphics with lm relation, and I want to archive and to plot for each one of them an equation y=ax+b with R². How can I do it?

lmfit <- geom_smooth(method="lm", se =开发者_如何转开发 T)

p <- qplot(x, y, data=Tab) + facet_grid(id ~., scales = "free") + lmfit

Within ggplot, there is no direct way to do this. You need to compute the regressions separately for each id and then extract the equation and R^2 from each of those. Put those extracted versions in a dataframe (along with id) and use geom_text to display them.