[R] Two-sided log axis

[John Wiedenhoeft]

Hi,

I have two curves that are best displayed using a logarithmic y-axis. I want 
to plot the difference of these curves, which means I would need a log scaling 
on both the negative and the positive side (i.e. the y-axis should be -100 -10 
-1 0 1 10 100). Zero values should not be discarded.

Is there an easy way to do that?

Thanks,
John