RE: Problem on subsampling gridded field onto point data locations

[ansley@xxxxxxxxxxxxx (Ansley Manke)]

Hi Haijun,

Thanks for bringing this up!

The SAMPLEXY function is being expanded to do the exact thing you are trying.
It had been too simplistic - limited only to choosing points which were on the 
grid of the data field and not interpolating to the points (X,Y) that you  
specify.  Your Ferret script looks fine.

The new SAMPLEXY function will come out with Ferret 5.1 within a few weeks.

Ansley Manke


Haijun Yang wrote 
> Date: Tue, 31 Aug 1999 
> 
> Hi, all,
> 
> I am learning to subsampling gridded field onto point data times. I did the following thing 
> based on Ferret documentation(V5.0) in the chapter entitled "Chapter 7A: WORKING WITH SPECIAL 
> DATA SETS" section 2.3:
> 
> yes? use coads_climatology
> yes? let my_lon=lon[d=my_data_file.dat]
> yes? let my_lat=lat[d=my_data_file.dat]
> yes? let sst_xy=samplexy(sst,my_lon,my_lat)
> 
> The file "my_data_file.dat" is
> 
>     index  longitude  latitude
>       1       150         0
>       2       150        2.5
>       3       150         5
>       4       150        7.5
>       5       150        10
>       6       157.5      12.5
>       7       165        15
>       8       172.5      17.5
>       9       180        20
>      10       187.5      22.5
>      11       195        25
>      12       202.5      27.5
>      13       210        30
> 
> So "my_lon" and "my_lat" are respectively,
> 
>     150,150,150,150,150,157.7,165,172.5,180,187.5,195,202.5,210
>      
>       0,2.5,  5,7.5, 10, 12.5, 15, 17.5, 20, 22.5, 25, 27.5, 30
>       
> The variable sst_xy should have a 2-D structure with index by 12 months.
> 
> But when I list sst_xy, it gives
> 
> yes? list sst_xy
>              SAMPLEXY(SST,MY_LON,MY_LAT)
>              DATA SET: /usr5/navyang/FERRET/FER_DSETS/data/coads_climatology.cdf
>                     1   2   3   4   5   6   7   8   9   10  11  12  13  
>                      1   2   3   4   5   6   7   8   9  10  11  12  13
>  16-JAN      /  1:....................................................
>  15-FEB      /  2:....................................................
>  17-MAR      /  3:....................................................
>  16-APR      /  4:....................................................
>  16-MAY      /  5:....................................................
>  16-JUN      /  6:....................................................
>  16-JUL      /  7:....................................................
>  16-AUG      /  8:....................................................
>  15-SEP      /  9:....................................................
>  16-OCT      / 10:....................................................
>  15-NOV      / 11:....................................................
>  16-DEC      / 12:....................................................
> 
> 
> Can anyone tell me what's wrong with the aboved process?
> 
> Thanks a lot in advance.
> 
> Haijun Yang
> 
> 
> ================================================
> Dept. of Atmospheric and Oceanic Sci.
> Univ. of Wisconsin-Madison
> 1225 West Dayton St.
> Madison, WI 53706
> ================================================
>