Re: [netcdfgroup] inquire number of dims visible from a group

• To: "David W. Pierce" <dpierce@xxxxxxxx>, <netcdfgroup@xxxxxxxxxxxxxxxx>
• Subject: Re: [netcdfgroup] inquire number of dims visible from a group
• From: "Pedro Vicente" <pedro.vicente@xxxxxxxxxxxxxxxxxx>
• Date: Sun, 21 Oct 2012 01:53:45 -0700

I use this function to get the group ID 
int nc_inq_grp_full_ncid(int ncid, char *full_name, int *grp_ncid);

then this function to get the number of dimensions

int nc_inq_dimids(int grp_ncid , int *ndims, int *dimids, int include_parents);

Note here that the first parameter of this function has to be  "grp_ncid" , not 
"ncid"  ( "ncid"  is the id obtained with nc_open )

so

nc_inq_dimids(grp_ncid , ndims, NULL, 0 );

gets the number of dims defined in this group

nc_inq_dimids(grp_ncid , ndims_parents, NULL, 1);

gets the number of dims defined in this group and parents (last parameter is 1 
instead of 0, and the third parameter  for "dimids"  is NULL  )

Pedro



  ----- Original Message ----- 
  From: David W. Pierce 
  To: netcdfgroup@xxxxxxxxxxxxxxxx 
  Cc: Mark Payne 
  Sent: Saturday, October 20, 2012 9:51 PM
  Subject: [netcdfgroup] inquire number of dims visible from a group


  Hello netcdf group,

  I'm running into odd behavior when trying to determine the number of dims 
visible from a group.

  The file has 2 dims defined in the root group, then a sub-group with a var 
that uses those 2 dims. When processing the file, I need to be able to 
determine how many dims are visible from the sub-group (in this case, 2). 

  The documentation for routine 

int nc_inq_dimids(int ncid, int *ndims, int *dimids, int include_parents)Says:

    dimids 
    An already allocated array of ints when the dimids of the visible 
dimensions will be stashed. Use nc_inq_ndims to find out how many dims are 
visible from this group. (see nc_inq Family). 
  However, when I actually use nc_inq_ndims, passing in the group ID, it 
doesn't return 2 (the number of dims visible from that group), it returns 0 
(the number of dims defined in that group). There doesn't seem to be any member 
of the nc_inq family of calls that takes an "include_ parents" parameter, which 
would handle this case.

  So, it seems like either:

  1) The documentation is a bit off, but in that case, how are you supposed to 
figure out the number of dims visible from a group? (I will note that this 
could easily be handled if nc_inq_dimids did not attempt to fill array dimids 
if dimids==NULL).

  2) The documentation is describing what the code is supposed to be doing, but 
the code doesn't actually implement this correctly.

  I'm using netcdf library version 4.2.1.1.

  Any suggestions?

  Regards,

  --Dave

  -- 
  David W. Pierce
  Division of Climate, Atmospheric Science, and Physical Oceanography
  Scripps Institution of Oceanography, La Jolla, California, USA
  (858) 534-8276 (voice)  /  (858) 534-8561 (fax)    dpierce@xxxxxxxx




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