[ferret_users] seasonal mask

["Prasad Thoppil (Forn-Natl)" <thoppil@xxxxxxxxxxxxxxx>]

I know this is rather a simple question. Suppose I have 50 years
(1948-1997) of daily time-series of wind speed, how do I find average
only for selected years. That is out of 50 years I want to find average
for 6 years such as

Let strong = {1950,1965,1966,1970,2000,2005}
Then apply a mask if year_of_wind EQ strong THEN wind 

Though I tried my logic, I could not get it right. 

Once I have a masked time-series, it is possible to find 6 year mean
(daily) by 
def axis/t=1-jan-0000:31-dec-0000:1/unit=days taxis
let strong_avg = wind[gt=taxis@MOD]

Thanks

Prasad