[ferret_users] problem with 'SAMPLEXY'

[Ms Sindu Raj Parampil <parampil@xxxxxxxxxxxxxxxxxx>]

Dear Ferreters,
I'm facing a problem with the function SAMPLEXY as I use it to pick out 
values from a gridded dataset (eg wind speed).

I have xpts and ypts from Jan-Dec and I select the lat,lon points
in 2 ways: 1) Jan-Dec and 2) May-Oct.

The wind values I obtain when I select xpts & ypts from Jan-Dec are 
different from when they are selected only for May-Oct.
Please see my script below.

1. Why isnt the wind during May-Oct in both cases identical? &
2. Why does the May-Oct selection give me wind data from Jan-Dec?

Am I missing something important while selecting the lat and 
lon points in time and using it in combination with SAMPLEXY ?

Thanks
Sindu

------ script-----------------------------------------------

let xpts_jan-dec = longitude[t="01-jan-2006:00:00":"31-dec-2006:00:00] 
let ypts_jan-dec =  latitude[t="01-jan-2006:00:00":"31-dec-2006:00:00]
let winds_jan-dec = SAMPLEXY(wind,xpts_jan-dec,ypts_jan-dec)

let xpts_may-oct = longitude[t="01-may-2006:00:00":"31-oct-2006:00:00] 
let ypts_may-oct =  latitude[t="01-may-2006:00:00":"31-oct-2006:00:00] 
let winds_may-oct = SAMPLEXY(wind,xpts_may-oct,ypts_may-oct)

------ script-----------------------------------------------


Sindu Raj Parampil
Ph.D Student
Centre for Atmospheric and Oceanic Sciences
Indian Institute of Science
Bangalore-12
INDIA
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