plot/lm/abline

Hi,

when I run

plot.default(z1, z2, xlab = "x", ylab = "y", main = "xxxx", pch = "+")
abline(lm(z1 ~ z2))

then the plot is plotted perfectly (scatterplot), however, the lm()
function doesnt appear on the plot. What could be wrong?

(Yesterday it worked perfectly, with the lm() line.)

Running R 2 on OS X.

Mathias Hunsk??r Furevik
Norway