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20000628: Help needed with _FillValue attribute in NetCDFPerl

Linda,

> To: address@hidden
> cc: address@hidden,
> cc: address@hidden
> From: Linda Wharton <address@hidden>
> Subject: Help needed with _FillValue attribute in NetCDFPerl
> Organization: NOAA/FSL
> Keywords: 200006282031.e5SKVxT26774

In the above message, you wrote:

> I am trying to set the _FillValue of an unlimited character array to "NONE"
> using NetCDFPerl and receive the following error:
> 
> ncvarput: ncid 3: Not a netCDF data type
> 
> Here is the code:
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> use NetCDF;
> 
> my $flname = "";
> my $Num_Pireps = "UNLIMITED";
> my $Str3 = 1;
> my $Str4 = 256;
> 
> $flname = "xyz.ncf";
> $ncid = NetCDF::create($flname , NetCDF::CLOBBER);
> NetCDF::setfill($ncid, NetCDF::FILL);
> 
> # Define diminsions.
> 
> $numpirID = NetCDF::dimdef($ncid, "Num_Pireps", $Num_Pireps);
> die "Couldn't define numPireps diminsion\n" if $numpirID < 0;
> 
> $str3ID = NetCDF::dimdef($ncid, "Str3_Lngth", $Str3);
> die "Couldn't define third diminsion\n" if $str3ID < 0;
> 
> $str4ID = NetCDF::dimdef($ncid, "Str4_Lngth", $Str4);
> die "Couldn't define forth diminsion\n" if $str4ID < 0;
> 
> # Define variables and attributes.
> 
> $pitypeID = NetCDF::vardef($ncid, "pirep_type", NetCDF::CHAR, [$numpirID, 
> $str3ID]);
> $N = "N";
> $attid = NetCDF::attput($ncid, $pitypeID, "_FillValue", NetCDF::CHAR, \$N);
> 
> $rawID = NetCDF::vardef($ncid, "raw_pirep", NetCDF::CHAR, [$numpirID, 
> $str4ID]);
> $attid = NetCDF::attput($ncid, $rawID, "long_name", NetCDF::CHAR, "Raw 
> Pirep");
> 
> $attid = NetCDF::attput($ncid, $rawID, "_FillValue", NetCDF::CHAR, "NONE");
> 
> NetCDF::endef($ncid);
> 
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> I have tried:
> 
> $nn = "NONE\0";
> $attid = NetCDF::attput($ncid, $rawID, "_FillValue", NetCDF::CHAR, \$nn);
> 
> and 
> 
> $nn = "NONE\0";
> $attid = NetCDF::attput($ncid, $rawID, "_FillValue", NetCDF::CHAR, $nn);
> 
> and 
> 
> $nn = 'NONE';
> $attid = NetCDF::attput($ncid, $rawID, "_FillValue", NetCDF::CHAR, \$nn);
> 
> and
> 
> $attid = NetCDF::attput($ncid, $rawID, "_FillValue", NetCDF::CHAR, 'NONE');
> 
> They all give the same error, which occurs as soon as the UNLIMITED dimension
> expands to the first slot and tries to do the fill value.  If I comment out
> the _FillValue line, the code works.  Attached is the output file after the
> error occurs.
> 
> 
> 
> I successfully executed the following $ptypeID code, with a one character
> _FillValue, but it doesn't work with trying to _FillValue with a longer 
> string:
> 
> $N = "N";
> $attid = NetCDF::attput($ncid, $pitypeID, "_FillValue", NetCDF::CHAR, \$N);
> 
> 
> Can you please tell me what I'm missing, and perhaps where it's covered in 
> the 
> documentation?
> 
> Thanks,
> 
> Linda Wharton
> Forecast Systems Lab, Boulder
> address@hidden
> 303-497-7239

The fill-value for a netCDF character variable is, necessarily, a single
character value: multi-character strings won't work.  If you want a
fill-value that is other than the default fill-value for characters,
then I suggest that you pass-in the integer value of the character you
want for the fill-value.

Regards,
Steve Emmerson   <http://www.unidata.ucar.edu>