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

[Dave Allured - NOAA Affiliate]

Also did you see my previous answer here?
http://mailman.ucar.edu/pipermail/ncl-talk/2017-November/010745.html

--Dave


On Fri, Nov 17, 2017 at 12:07 PM, Adam Phillips <asphilli at ucar.edu> wrote:

> Hi Jiali,
> I believe Dennis answered this question a few days ago:
>
> x[*]   with _FillValue attribute
>
>  ;nmsg = num(ismissing(x))   ; coun number of missing
>
>   igood = ind(.not.ismissing(x))
>   xgood = x(igood)
>   print(xgood)
>
> You need to use the ind function to identify what isn't missing, and then
> pass those indices to your st1, lon1 and lat1 arrays.
> good = ind(.not.ismissing(st1))
> st2 = st1(igood)
> lat2 = lat1(igood)
> lon2 = lat2(igood)
>
> Adam
>
> On Fri, Nov 17, 2017 at 11:04 AM, Wang, Jiali <jialiwang at anl.gov> wrote:
>
>> 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 <(630)%20252-2848>
>>
>> http://www.evs.anl.gov/about-evs/staff/detail/index.cfm?/Wang/Jiali
>>
>
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