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) Fax:+91-40-25503596(O) E-mail:sjo@rediffmail.com; callsjo@yahoo.com; sjo@incois.gov.in. Web- http://oppamthadathil.tripod.com *************************************** _________________________________________________________________ NRIs - Free money transfer to India. Fly to India for free! http://acm.bridgeovertw.com/hdfc/qr/landingpage/sep04/index.htm?sitecode=610|394 Apply Now. |