Dear Tim CF standard names require canonical units, so it would not be possible to have a standard name for a data variable whose elements did not all have the same units. I suspect that in various places we have tacitly assumed that units is a scalar string, as you say.
Your question is a bit like other ones which have come up about how we might group various data variables that belong together, such as elements of a vector, which also might not have the same units (if in a radial coordinate system, for example) and have different standard names. We haven't agreed a way to do that, but there have been ideas about using another variable to contain a list of variable names. Maybe you could use a method like that. Best wishes Jonathan ----- Forwarded message from Timothy Patterson <[email protected]> ----- > Date: Wed, 6 Apr 2016 17:07:33 +0000 > From: Timothy Patterson <[email protected]> > To: "[email protected]" <[email protected]> > Subject: [CF-metadata] Multiple units attribute for an array of polynomial > coefficients > > I have a set of measurement data to which I fit a polynomial and store the > coefficients in a single netCDF file along with other information. > > The degree of the polynomial is not always the same, so for flexibility I > planned to store the coefficients in a single array variable rather than as > separate variables so that I have one format that handles any degree of > polynomial. > > As I'm fitting measurement data, the coefficients have associated units. If I > stored the data as individual variables, I could attach these values via a > "units" attribute, but I'm storing the values in an array. However, an > attribute can be a vector of values so in theory it could be possible to > define a vector "units" attribute of the same length as my array dimension > and thereby associate a different unit value to each coefficient. > > I think this probably violates the CF conventions and that when the > conventions state - "The value of the units attribute is a string" - that I > should interpret that as meaning a single string and not a vector of strings. > > Is there a better and CF-compliant way to handle this, or should I just > resign myself to the fact that if I want the flexibility of an array > variable, the users will have to work out the units for themselves? > > Thanks! > > Tim > > > _________________________________________________________________________________________ > Dr. Tim Patterson > Instrument Data Simulation Expert > Product Engineering/Test Data Coordination > MTG Programme > GEO Division > > EUMETSAT > Eumetsat-Allee 1 > 64295 Darmstadt > Germany > > Tel: +49 6151 807 487 > Fax: +49 6151 807 7 > E-mail: [email protected] > Web: www.eumetsat.int > > > > > > > Any email message from EUMETSAT is sent in good faith but shall neither be > binding nor construed as constituting a commitment by EUMETSAT, except where > provided for in a written agreement or contract or if explicitly stated in > the email. Please note that any views or opinions presented in this email are > solely those of the sender and do not necessarily represent those of > EUMETSAT. This message and any attachments are intended for the sole use of > the addressee(s) and may contain confidential and privileged information. Any > unauthorised use, disclosure, dissemination or distribution (in whole or in > part) of its contents is not permitted. If you received this message in > error, please notify the sender and delete it from your system. > _______________________________________________ > CF-metadata mailing list > [email protected] > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata ----- End forwarded message ----- _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
