[R] Trend lines on a scatterplot matrix

[Alan S Barnett]

I'm using pairs() to generate a scatterplot matrix;

pairs(~ Fuzzy.gray.white.ratio+Fuzzy.gw.t.score+AgeWhenTested+signal_mean.noise,
	data=datam,subset=status=="control",main="Controls",
        labels=c("G/W","Peak Separation","Age","S/N"))


How can I add regression lines to the plots?