[R] adding a reference line to an xyplot

Hi, I want to add a dashed vertical line to a number of xyplots. Here is a simple script of the type of plot I have but then I want to add a reference line to 1995 on each of the panels. I have tried panel.abline and other suggestions on the forum but can't get it to work.

[R] Orthogonal polynomial contrasts

How do you remove one of the terms from an ordered polynomial contrast in your linear model. For example, I have significant terms for linear and cubic but not quadratic, how would i remove the quadratic term from lm(response~treatment) Cheers, Chris -- View this message in context: