Re: how to use the MISSING function (next mail)

[Ansley Manke <ansley.b.manke@xxxxxxxx>]

Hi -
If the value 9.969210E+36 is marked as the missing-value
flag in your netCDF file, then Ferret should recognize it as the
missing value.  If you do the Unix command ncdump you will
see the missing_value and/or the Fill_value attribute listed with
your variable in the header. Ncdump of the file uses the symbol _
to denote missing data. For example, the section of the ncdump
output that describes SST in the coads_climatology dataset shows
both a missing_value and a _FillValue:

> ncdump coads_climatology.cdf  | more

netcdf coads_climatology {
dimensions:
   COADSX = 180 ;
   COADSY = 90 ;
   TIME = UNLIMITED ; // (12 currently)
variables:
   double COADSX(COADSX) ;
...
   float SST(TIME, COADSY, COADSX) ;
       SST:missing_value = -1.e+34f ;
       SST:_FillValue = -1.e+34f ;
       SST:long_name = "SEA SURFACE TEMPERATURE" ;
       SST:history = "From coads_climatology" ;
       SST:units = "Deg C" ;
...

I don't know why Ferret would have a problem with the missing
value in your file, but if you like, you can use the MISSING
function to replace the flag associated with your variable

  ! Get the default missing-data flag, defined automatically for any 
variable

  let a = 12
  let missing_default = `a, RETURN=bad`

  ! define a new variable that has the co2 data, but the default 
missing flag

  let co2_default =  MISSING(co2, missing_default)

Ansley

Yogesh K. Tiwari wrote:

> Hi,
>
> Just I want to add little on my question regarding above subject.
>
> I read all the netcdf files in fortran code, and actually the fortran 
> output shows that the missing values are filled by the number :
>
>   9.969210E+36
>
> not by any special sign -'
>
> My question is :-
>
> Whether ferret likes this number 9.969210E+36 as missing value.
>
> If not then how we can change this number which ferret likes as 
> missing flag , I think -1e34.
>
> Kindly help,
>
> Regards,
> Yogesh
>
>
>
> Yogesh K. Tiwari wrote:
>
> > Hello Ferret Users,
> >
> > I have the data which has the missing values and the data looks like :
> >
> > co2 =   _, _, _, _, _, _, _, _, _, _, _, _, _, _,
> >         _, _, _, _, _, _, _, _,
> >         _, _, _, _, _, _, _, _, _, _, _, _, _, _,
> >         _, 368.8943, 368.894, 368.9885,368.9885,
> >        368.9885, 368.8637, 368.874,368.8583,
> >        368.8586, 368.894, 368.9882, 368.9879,
> >        368.9879, 368.8361,368.874, 368.8581, _,
> >        _, _, _, _, _, _, _, _, _, _, _, _, _, _,
> >        _, 372.2896,
> >
> >
> >
> > Here as we can see the missing value is denoted by
> > the special sign  -'
> >
> > Is there any way that we can fill this missing value by the ferret 
> > default missing value -1e34
> >
> > I am doing some analysis in ferret and ferret dosen't like this above 
> > missing value and from last four days its in hanging position.
> >
> > If I am using the data which dosen't have the missing value, means 
> > the data looks like :
> >
> > co2 = 382.7223, 372.0434, 369.4157, 378.8927,
> >        373.9405, 378.7924, 380.5195,374.1316,
> >        379.1323, 380.9348, 372.5852, 378.6689
> >
> > Then my script works fine and ferret gives the result within few minuts.
> >
> > Here the script is attched which I am using for the above data.
> >
> > Kindly help.
> >
> > The imediate help would be appreciated much.
> >
> > Regards,
> > Yogesh
> >
> >
> >
> > ------------------------------------------------------------------------
> >
> > !NOTE :- the following script works fine for the
> > !         data points which has no gaps as :
> >  
> > !          371.232, 368.224, 371.232, 368.224, !
> > !         and ferret calculations gives !         the answere within 
> > few minuts          !         BUT if !         there is gap in 
> > between the data points
> > !         like
> > !         -' -' -' 370.232, 368.224, -'-'-'-'
> >
> > !         then ferret dosen't gives any answere !         even if it 
> > is working 4-5 days continue.
> > !****************************************************
> >
> >
> > ! open datasets
> >
> >      set data run_94/ecmwf_co2_jul2003.nc  ! keep the order of datasets
> >      set data tm3airs_new_July_2003.nc   !   unchanged
> >
> > ! define destination axes from lat and lon in ecmwf_co2_jan2003
> >
> >      define axis/x/units=longitudes/from_data xlon=lon[d=1]
> >      define axis/y/units=latitudes/from_data  ylat=lat[d=1]
> >      define grid/x=xlon/y=ylat gcom
> >
> > ! regrid the tm3co2 in tm3airs_new_January_2003.nc  to the above grid 
> > using scat2grid
> >
> > ! define the radius and cutoff values for scat2grid function
> >
> >      define symbol radius = 0.25   ! ideal values for a 0.25 grid
> >      define symbol cutoff = 2.0    !  with possible minimum 
> > interpolation errors
> >
> >      let lon_1D   = XSEQUENCE(lon[d=2])
> >      let lat_1D   = XSEQUENCE(lat[d=2])
> >      let co2_1D   = XSEQUENCE(tm3co2[d=2])
> >
> > !define the function to count the observed value in each 1x1 grid
> >
> >      let obs_count = 
> > scatgrid_nobs_xy(lon_1D,lat_1D,x[gx=gcom],y[gy=gcom])
> >
> > !griding tm3co2 using the mask if there is atleast 10 observations in 
> > one grid
> >
> >      let co2_point = IF obs_count GE 10 THEN\
> >                      scat2gridgauss_xy(lon_1D,lat_1D,co2_1D,\
> >                      
> > x[gx=gcom],y[gy=gcom],($radius),($radius),($cutoff),($cutoff))
> >                     
> > !     shade co2_point
> >
> >
> > sp rm -f airs_jul_grided_point_data.nc
> > save/file=airs_jul_grided_point_data.nc/append  co2_point