Drawing the equator

[Mark Williams <mark.williams@xxxxxxxxxx>]

Dear Ferret users

Can anyone tell me a quick way to draw a line across a plot to show where x 
or y is zero when it's not on the boundary of the plot?  For example the 
equator on a plot which extends from 30s to 30n north or where U = 0 on a 
plot which has the y axis extending from -20 to 20?

Thanks a lot.

Mark

Mark Williams
Supervising Meteorologist
Victorian Regional Office
ph 61 3 9669 4902