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

• To: Pedro Vicente <pedro.vicente@xxxxxxxxxxxxxxxxxx>
• Subject: Re: [netcdfgroup] inquire number of dims visible from a group
• From: "David W. Pierce" <dpierce@xxxxxxxx>
• Date: Sun, 21 Oct 2012 17:03:34 -0700

Thanks. That seems to work. Documentation bug for routine nc_inq_dimids() I
guess.

Regards,

--Dave

On Sun, Oct 21, 2012 at 1:53 AM, Pedro Vicente <
pedro.vicente@xxxxxxxxxxxxxxxxxx> wrote:

> **
>
>
> 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 <dpierce@xxxxxxxx>
> *To:* netcdfgroup@xxxxxxxxxxxxxxxx
> *Cc:* Mark Payne <mpa@xxxxxxxxxxx>
> *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<http://www.unidata.ucar.edu/software/netcdf/docs/netcdf-c/nc_005finq-Family.html#nc_005finq-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 <%28858%29%20534-8561> (fax)
> dpierce@xxxxxxxx
>
>  ------------------------------
>
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>


-- 
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

• References:
  • [netcdfgroup] inquire number of dims visible from a group
    • From: David W. Pierce
  • Re: [netcdfgroup] inquire number of dims visible from a group
    • From: Pedro Vicente