Heng,
On Wed, May 13, 2015 at 3:29 AM, Choo Heng Kek <hengkek@xxxxxxxxxx> wrote:
> Dear colleagues
> Probably silly questions but...
>
All good questions.
> Is it possible to have metadata/attributes for Dimensions?
>
Not directly, in the Netcdf data model.
We are creating netcdf files and wish to describe the sometimes cryptic'ly
> named Dimension variables somewhere in the netcdf file itself (since it's
> supposed to be self-describing). We could put it in the Global Attributes
> section but that may be too "far away" from where the Dimension variables
> are located in the ncdump output.
>
I know what you mean my "too far away", but global attributes might be the
best choice for such documentation. I suggest that you use a separate
character attribute for each dimension that you need to describe.
Here are some alternatives. I prefer #1 and #3:
1. Make up dimension names that are less cryptic and more relevant. One
example that I have used is "min_max" for a fixed dimension of size 2,
where x(:,:,0) is minimum value statistics, and x(:,:,1) is maximum value
statistics at various time steps and levels.
2. For any dimension that has an associated coordinate variable, you could
put the documenting attribute on that coordinate variable:
netcdf y {
dimensions:
...
nn = 44;
variables:
...
integer nn(nn) ;
nn:dimension_meaning = "polynomial exponent number" ;
3. For any dimension that has an associated coordinate variable, a
conventional descriptive attribute for the coordinate variable will
probably be most appropriate. The distinction between the dimension and
the coordinate variable is merged. For example:
level:long_name = "isobaric pressure level"
Also, is it bad practice to type long-winded descriptions in Attributes as
> in the example below?
>
No, this is good practice in my opinion. Especially good for all those
natural Latin speakers out there. ;-)
> """
> netcdf y {
> dimensions:
> latitude = 157 ;
> longitude = 288 ;
> time = UNLIMITED ; // (61 currently)
> nn = 44; // Any way to provide more description of this dimension?
> variables:
>
> ...
> float DIRSW_surface(time, latitude, longitude) ;
> DIRSW_surface:_FillValue = 9.999e+20f ;
> DIRSW_surface:short_name = "DIRSW_surface" ;
> DIRSW_surface:long_name = "Secondary Wave Direction" ;
> DIRSW_surface:units = "deg" ;
> DIRSW_surface:notes = "this is an example of a long
> attribute to explain in greater detail what this variable is about. Sit an
> nominavi eloquentiam. Ad decore signiferumque mea. Nostrud ocurreret
> salutatus id sit. Ferri assueverit no vim. Vix ea labore scribentur, pri
> integre nonumes eligendi in, id duo veniam honestatis. Eu eruditi delectus
> pri. Labores veritus blandit te mei. Id reque utroque euripidis pro.
> Moderatius argumentum in vix, cu cum mucius maluisset forensibus, enim
> audire utamur ius eu. Ei illud porro congue eum, ei nec errem putent
> atomorum. Ut ridens blandit eos, ne reque suavitate mel. Et duo consul
> essent persequeris. Ne wisi facilis vis, maiorum singulis vis an. At eum
> solum justo, verear dolores similique quo ut, graece aliquid cotidieque ad
> quo. Duo an facete voluptatum." ;
> }
> """
>
--Dave
