tmpar <- par(mar=c(3.1,3.1,0,0),pty="s")

mplot(predict(leprosy.fit),resid(leprosy.fit),group=leprosy$drug,
	xlab="",ylab="")
mtext("predicted",1,2)
mtext("residual",2,2)
abline(h=0,lty=2)
abline(h=c(-1,1)*std.dev(leprosy.fit),lty=3)

par(tmpar)