Re: [netcdfgroup] defining dimensions in groups

• To: Pedro Vicente <pedro.vicente@xxxxxxxxxxxxxxxxxx>
• Subject: Re: [netcdfgroup] defining dimensions in groups
• From: Dennis Heimbigner <dmh@xxxxxxxxxxxxxxxx>
• Date: Fri, 18 Jan 2013 14:59:23 -0700

1. The inner dimension is used. The rule is to look up the group tree
   from innermost to root and choose the first one that is found
   with a matchng name.
2. The fact that it is a dimension for a coordinate variable is not relevant 
for the
   choice.
However, note that this rule is only used by ncgen when disambiguating a 
reference
in the CDL.  The issue does not come up in the netcdf API because
you have to specifically supply the dimension id when defining the dimension
for a variable.

The rule is implemented in the ncgen parsing code. I can tell you specifically
where if you really want to know.

=Dennis Heimbigner
 Unidata


Pedro Vicente wrote:

Hello everyone

I have a couple questions regarding the definition of dimensions in groups;

Consider the following CDL definition

netcdf in_grp {
dimensions:
 lon=3;
variables:
 //coordinate variable
 float lon(lon);
data:
 lon=1,2,3;

group: g1 { dimensions:

 lon=2;
 variables:
 float lon(lon);
 float data(lon)
 data:

lon=1,2; } // end g1

} // end

There is a "lon" dimension/coordinate variable both at root and in group /g1 and they 
have different dimensions, so variable named "data" has 2 dimensions with the same name 
in scope,
and somehow has to choose one

Just wanted to confirm

1) Is this definition legal?

2) What is the algorithm that the netCDF library uses to distinguish between both dimensions in scope for the variable /g1/data? 3) Defining "lon" as a coordinate variable instead of just a dimension name, does this definition has any consequence for the way this is handled by the library for this case?

Can someone from Unidata please point me to the location in the source code 
where this is handled?

thanks Pedro

----------------------
Pedro Vicente
http://www.space-research.org/





------------------------------------------------------------------------

_______________________________________________
netcdfgroup mailing list
netcdfgroup@xxxxxxxxxxxxxxxx

For list information or to unsubscribe, visit: http://www.unidata.ucar.edu/mailing_lists/

• Follow-Ups:
  • Re: [netcdfgroup] defining dimensions in groups
    • From: Pedro Vicente

• References:
  • [netcdfgroup] defining dimensions in groups
    • From: Pedro Vicente