Re: 980323: C++/netcdf-3.4

>To: address@hidden
>From: CHEUNG WENDY WAI WAN <address@hidden>
>Subject: C++/netcdf-3.4
>Organization: .
>Keywords: 199803230217.TAA20025

Hi Wendy,

> I'm a engineering grad student at CU and I have a potentially simple
> problem.
> 
> My model requires variables to be double precision. I have been playing
> with the 'example.cc' program in the /netcdf-3.4/src/cxx directory. In the
> code, I make 2 simple substitutions: float(NcFloat) with double (NcDouble) 
> 
> 1(line 25)    NcVar* P = nc.add_var("P", ncDouble, frtimed, latd, lond); 
> 
> 2(line 73)    static double P_data[] = {
> 
> and I get the following error:
> 
> ncvarput: ncid 3: Not a netCDF data type or _FillValue type mismatch

Just also change line 30 from

     P->add_att("_FillValue", -9999.0f);
to
     P->add_att("_FillValue", -9999.0);

to make the _FillValue attribute of the same type as the variable, and
things should work fine.  It's not necessary to define a _FillValue
attribute for variables, but when you do, its type must agree with the
type of the variable.  The C++ interface doesn't have an explicit type
parameter for defining attributes, but instead just uses the type
corresponding to the value to create an attribute of the appropriate
type, and in this case the float type of the constant "-9999.f" cause it
to create an attribute of type NcFloat which disagreed with the NcDouble
type of the variable.

--Russ

_____________________________________________________________________

Russ Rew                                         UCAR Unidata Program
address@hidden                     http://www.unidata.ucar.edu