abline() with xyplot()

Hello all,
I'm a new user on R, and I used the abline function to draw a line on
my graph but it doesn't work with xyplot(). With the plot function,
abline() is ok but with plot it doesn't make what I want. Maybe it's
a little thing to change in plot() but I don't find what! With xyplot
I write this :
Xyplot(m~ordered(l,levels=1),
type="b",xlab="lagdist",ylab="Moran'I",lty=1,lwd=2,cex=1.5,pch=pch)
Abline(h=0,lty=2)

I'm not aware of anything called 'Xyplot' or 'Abline' (note that R is 
case sensitive).

There's no error message but no line too.
If someone see my error or know how to do, thanks in advance.

'xyplot' is part of a graphics system that is different from standard R 
graphics. If you want to use it, you first need to learn how. 
help(Lattice) has some pointers that should get you started. 

In this case, you probably want something like

xyplot(m ~ ordered(l, levels=1),
       type="b", xlab="lagdist",
       ylab="Moran'I", lty=1, lwd=2, 
       cex=1.5, pch=pch, 
       panel = function(...) {
           panel.abline(h = 0, lty = 2)
           panel.xyplot(...)
       })

-Deepayan