How to create a a scalar NetCDF variable (i.e with no dimensions)?

I need to define a NetCDF variable with a dimension of size zero. The NetCDF function, netcdf.defVar requires a dimid, but it is not possible to define a dimension of length zero, since assigning zero in netcdf.defDim produces an unlimited dimension. Does matlab have any native functions to support zero length variables?

Answer 1

[Ashish Uthama]

Could you tell us why would you need a dimension of size zero?

Are you trying to create a scalar variable? If so, try [] for the dimid in the call to netcdf.defVar. (You could also try the newer nccreate if you have it.)

Answer 2

[Jonathan Blythe]

Thank you, this did the trick.

We use 'empty' NetCDF variables to tack ancillary metadata. In this case, the Climate and Forecast conventions specify a variable called Grid Mapping that is one instance of this.

[Mary Jo Brodzik]

I needed to do this same task and it took me a long time to come across this answer. One additional note for others who may also be puzzled: for the CF grid_mapping variable, you only need to define the variable and then add the projection attributes, no need to use 'putVar' to populate it with anything degenerate, e.g.:

varid = netcdf.defVar(ncid, 'crs', 'NC_INT', []);
netcdf.endDef(ncid);
netcdf.putAtt(ncid, varid, 'grid_mapping_name', 'sinusoidal');
% ...then use putAtt for the rest of the 'crs' attributes