[ncl-talk] Removing missing values from a 1D data

[Wang, Jiali]

Dear NCL group,

I am having a similar question as this post https://www.ncl.ucar.edu/Support/talk_archives/2011/1499.html but unfortunately i didn't get it..

I have a 1D data set (station data) as shown below. I would like to filter out the lower orders (order smaller than 2). I do this using "where", so I get lots of missing values for those stations with lower orders. But these values take lots of space, so I want to get rid of them and output a much lighter data only for the stations with non-missing values. Below is what my data and my NCL script look like.  Could you please take a look and advice? With my script I am still having all the missing value in my output.

ncdump -c 200303091200.CHRTOUT_DOMAIN3
netcdf \200303091200 {
dimensions:
        station = 3678397 ;
        time = 1 ;
variables:
        float latitude(station) ;
                latitude:long_name = "Station latitude" ;
                latitude:units = "degrees_north" ;
        float longitude(station) ;
                longitude:long_name = "Station longitude" ;
                longitude:units = "degrees_east" ;
        float streamflow(station) ;
                streamflow:units = "meter^3 / sec" ;
                streamflow:long_name = "River Flow" ;
        int order(station) ;
                order:long_name = "Strahler Stream Order" ;
=============
a = addfile("200303101200.CHRTOUT_DOMAIN3"+".nc","r")
st = a->streamflow
lat = a->latitude
lon = a->longitude
ord = a->order ;;do filter based on this number, we only want order>2

st1 = new(dimsizes(st),typeof(st))
lat1 = new(dimsizes(lat),typeof(lat))
lon1 = new(dimsizes(lon),typeof(lon))

st at _FillValue = -9999
st1  = where(ord .gt. 2, st, st at _FillValue)
lat1 = where(ord .gt. 2, lat, st at _FillValue)
lon1 = where(ord .gt. 2, lon, st at _FillValue)

if (.not.all(ismissing(st1))) then   ;;I think this "if" statement has some problem, but I am not sure what's the right one should be..
    system("/bin/rm -f simple.nc")
    ncdf = addfile("simple.nc" ,"c")
    ncdf->streamflow = st1
    ncdf->lat        = lat1
    ncdf->lon        = lon1
;;;;;;or output in txt format
      opt = True
      opt at fout = "foo.txt"
      write_matrix(st1, "10f7.2", opt)
end if

==============

Thanks!

Jiali Wang, Ph. D
Environmental Science Division
Argonne National Laboratory
Tel: 630-252-2848
http://www.evs.anl.gov/about-evs/staff/detail/index.cfm?/Wang/Jiali

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