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Re: Comments

This archive contains answers to questions sent to Unidata support through mid-2025. Note that the archive is no longer being updated. We provide the archive for reference; many of the answers presented here remain technically correct, even if somewhat outdated. For the most up-to-date information on the use of NSF Unidata software and data services, please consult the Software Documentation first.

  • Subject: Re: Comments
  • Date: Thu, 13 Jan 1994 15:00:20 -0700
> Organization: River Forecast Center, TULSA
> Keywords: 199401131409.AA09924

Hi Nalneesh,

> I am new to this group and I have a very straight forward question. How do
> I put comments in the netcdf file. It seems that in the library there are
> no functions that allow that kind of operation, or may be I am not so
> thorough.

Comments must be represented as the values of attributes, either named
global attributes or variable-specific attributes.  There is no standard way
to represent the comments put in a CDL file after the "// " characters in
the netCDF file, since those comments don't necessarily apply to either a
particular variable or to the whole netCDF file (for example, they may apply
to a dimension, an attribute, or a group of variables).

General comments about all of the data in a netCDF file may be represented
using a string-valued attribute, such as:

        :Comments = "This data is known to be suspect.  Users who want\n",
                    "to know the details, should consult the paper by\n",
                    "    I. M. Dubious, 1999." ;

Comments about a dimension or attribute require some sort of convention,
since dimensions and attributes cannot have attributes in the netCDF data
model (only variables have attributes).  You could use global attributes
that include the dimension or variable/attribute name, for example:

        dimensions:
                rec = UNLIMITED;
        variables:
                float T;
                        T:calibration = "-3" ;
           ...
                :Comments_rec_dim = "This dimension is unlimited because\n",
                                    "we may eventually want to add more\n",
                                    "data for later times.\n" ;
                :Comments_T_var_calibration_att = "in Hobson units";

Also, in the future you may want to send netcdf questions to the Unidata
support address address@hidden, so they will be properly forwarded
to someone who can answer the question even if I am out of town or on
vacation.  Thanks.

--Russ
__________________________________________________________________________
                      
Russ Rew                                              UCAR Unidata Program
address@hidden                                        P.O. Box 3000
(303)497-8645                                 Boulder, Colorado 80307-3000