[netCDF #AKU-355464]: Coordinate axis values for an UNLIMITED dimension

Hi Jennifer,

> I would like to write out a netcdf file that has an unlimited dimension.
> The problem is that the resulting file does not contain values for that
> dimension -- they appear to be missing. I have attached below a modified
> version of press_temp_4D_wr.c, which was included in the library source
> code, and which creates a file with the following output from ncdump:
> 
> netcdf pres_temp_4D {
> dimensions:
> level = 2 ;
> latitude = 6 ;
> longitude = 12 ;
> time = UNLIMITED ; // (2 currently)
> variables:
> float longitude(longitude) ;
> longitude:units = "degrees_east" ;
> float latitude(latitude) ;
> latitude:units = "degrees_north" ;
> float level(level) ;
> float time(time) ;
> float pressure(time, level, latitude, longitude) ;
> pressure:units = "hPa" ;
> float temperature(time, level, latitude, longitude) ;
> temperature:units = "celsius" ;
> data:
> 
> longitude = -125, -120, -115, -110, -105, -100, -95, -90, -85, -80, -75, -70 ;
> 
> latitude = 25, 30, 35, 40, 45, 50 ;
> 
> level = 1, 6 ;
> 
> time = _, _ ;
> }
> 
> 
> How can I get it to write out the defined values for the time axis
> instead of "time = _, _ ;" ?
> 
> It will work if I change this:
> 
> nc_def_dim(ncid, REC_NAME, NC_UNLIMITED, &rec_dimid)
> to
> nc_def_dim(ncid, REC_NAME, NREC, &rec_dimid)
> 
> But then the dimension is no longer a record dimension.
> 
> --Jennifer

I suspect you are trying to write the time dimension with nc_put_var, rather 
than nc_put_vara().

See this note from the nc_put_var() documentation for why nc_put_var() won't 
work as expected 
until some record data has already been written to the file:

  Take care when using this function with record variables (variables
  that use the NC_UNLIMITED dimension). If you try to write all the
  values of a record variable into a netCDF file that has no record
  data yet (hence has 0 records), nothing will be written. Similarly,
  if you try to write all the values of a record variable but there
  are more records in the file than you assume, more in-memory data
  will be accessed than you supply, which may result in a segmentation
  violation. To avoid such problems, it is better to use the
  nc_put_vara interfaces for variables that use the NC_UNLIMITED
  dimension.

--Russ

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



Ticket Details
===================
Ticket ID: AKU-355464
Department: Support netCDF
Priority: Normal
Status: Closed