Dear Ed,
Firatly, this is reply to ticket #104 (Clarify the interpretation of
scalar coordinate variables), but I have moved to discussing scalar
coordinates to the general list, as I don't think it will be
constructive to clog up a third(!) trac ticket with this long running
debate. We can always move back there, of course, as we see fit.
> Given that the spec is not clear I suspect the interpretation we are
> debating may also be within user code rather than the libraries that
> load the data from file. Despite this I support your call for
> evidence so we can make an informed decision.
I think the remit should be wide:
Has anyone been actively using this interpretation, either in
their own code or with third part libraries?
I hope that we may find out.
> I'm intrigued that you think units, bounds and/or a positive
> attribute can combine to turn a scalar quantity into a vector
> quantity.
This goes to the heart of our disagreement. I see a CF-netCDF scalar
coordinate as merely a shorthand for a a size 1, 1-d coordinate. This
optional shorthand serves to remove the need to index data arrays
along dimensions which have no variation (i.e. they have size 1). I
very deliberately mentioned CF-netCDF since a CF-netCDF scalar
coordinate is not a scalar in the abstract sense. This is because it
explicitly applies to a dimension - albeit one which has been omitted
from the file for human convienince.
All the best,
David
--
David Hassell
National Centre for Atmospheric Science (NCAS)
Department of Meteorology, University of Reading,
Earley Gate, PO Box 243,
Reading RG6 6BB, U.K.
Tel : +44 118 3785613
E-mail: d.c.hassell at reading.ac.uk
Received on Tue Jun 18 2013 - 07:27:37 BST
