[ferret_users] lanczos function - retaining annual cycle signal in monthly time series

[Torben Mueller <torbenmllr@xxxxxxx>]

Dear Ferret Community,

I want to use the lanczos filter to remove any signal from a time series that is not the annual cycle. 
Regrettably, the documentation for the function is not very clear to me, especially in which units the low and high frequency cutoff points need to be given.
My time series has monthly data and I just want to keep the annual cycle. Which values should I choose for F1, F2 and N?

Thanks!

http://ferret.pmel.noaa.gov/Ferret/documentation/users-guide/appendix-a-external-functions/LANCZOS/