Hi Sudheer and Jaison,
The SAMPLEXY function works fine if the data is on irregular axes, but
it
does have the restriction that if the axis is MODULO then it must be
REGULAR.
(I imagine this restriction could be lifted with some clever
programming, but we
have not yet made the function that smart.)
Ansley
Jaison Kurian wrote:
Hi Sudheer,
You can use SAMPLEXY function to sample a variable
at desired lat-lon locations. From the usermanual
(Ch3 Sec2.3.34. SAMPLEXY )
SAMPLEXY(DAT_TO_SAMPLE,XPTS,YPTS) Returns data sampled at a
set of (X,Y) points, using linear interpolation.
SAMPLEXY is a "grid-changing" function; its output grid is
different from the input arguments. Therefore it is best
to use explicit limits on the first argument rather than a
SET REGION command.
I think SAMPLEXY works well only for regular (equaly spaced)
X & Y axis (especially if the LONGITUDE axis is flagged as
MODULO). Anyway if you are planning to use Levitus Climatology
you don't have to worry about this.
Please have a look at the example given below.
Hope this helps
With Regards
Jaison
...........samplexy_lev.dat...........
LAT LON
=== ===
9.0 68.4
10.2 72.6
8.5 70.2
7.2 65.5
...............................
!---------samplexy_lev.jnl-----------
! open climatology dataset
set data levitus_climatology
! open ascii file containing lat-lon points
! use "/SKIP" to skip header lines if any
file/skip=2/var="lat,lon" samplexy_lev.dat
! do the sampling using SAMPLEXY function
let temp_lev = SAMPLEXY(temp[d=1], lon[d=2], lat[d=2])
list/k=1:5 temp_lev
! assign proper title and units if you are saving this to a file
set var/title="Temperature Extracted from Levitus Climatology"/\
units="^oC" temp_lev
set var/title="Latitude of data points"/units=latitudes lat
set var/title="Longitude of data points"/units=longitudes lon
sp rm -f samplexy_lev.nc
save/file=samplexy_lev.nc/append temp_lev
save/file=samplexy_lev.nc/append lon,lat
!-----------------------------------------------
On Tue, 23 Nov 2004, Sudheer Joseph wrote:
Dear Users ,
Is there any way to extract data from a netcdf file at
specicifed( irregular) lat lon positions read from a file,
essentially I needed the following
file/var= lat,lon ll.dat
get temperature data from levitus data.cdf @ lat log
is there a method to get this data form the specified lat lon
thanks,
sudheer
***************************************
Dr. Sudheer Joseph
Indian National Centre for Ocean Information Services
Gajularamaram B.O., IDA Jeedeemetla S.O.
Via Pragathi Nagar, Kukatpally, Hyderabad
Pin:5000 55
Tel:+91-40-23044600(R)
Tel:+91-40-9440832534(Mobile)
Tel:+91-40-25503595(O)
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E-mail:sjo@rediffmail.com;
callsjo@yahoo.com;
sjo@incois.gov.in.
Web- http://oppamthadathil.tripod.com
***************************************
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