On 3/28/2012 6:26 AM, Jonathan Gregory wrote:
> Dear all
>
> Brian has a good point that sect 5.3 allows that there might be missing data
> in aux coord variables. Appendix A - which is equally ancient in the story of
> CF :-) - is not consistent with this, because it didn't allow _FillValue or
> missing_value atts for coordinates until sect 9 was introduced in version 1.6.
> But never mind the history, the point is to clarify what we need now.
>
> In Randy's, Rich's and Bert's examples, if I understand correctly, there are
> non-existent points, at which both data and aux coord vars are missing values.
> That is also what sect 9 requires. I don't see any problem with this.
>
> Nan's example is different, because it has missing values in aux coord vars
> at points where there is non-missing data. If we all agree that this is OK
> too, then fine. Speaking for myself, I could agree to it, but I'm less happy,
> because clearly the aux coord var is not doing its job of locating the data.
>
> I think you said, Nan, that you might fill them in at some later stage. At
> that stage, they should certainly be aux coord vars. Before they are filled
> in, of course I am not saying they should be excluded from the file, but I
> am asking if they should be regarded as data, rather than coordinates. A
> pressure value which was destined to be an aux coord var, but is actually a
> data variable measured by a sensor and has missing values in it, could be
> named by the ancillary_variables attribute. It is really per-point metadata,
> which is what ancillary_variables are
> (http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.5/cf-conventions.html#ancillary-data)
> but you could argue it should not be regarded as an aux coord var if it can't
> provide information for every point where there is data.
>
> I'm just asking. I don't have a very strong opinion about this, but I'd like
> to know if others have the same concern that I do.
>
> My existing ticket (85) connected with this subject is a defect ticket. It
> is only able to correct mistakes. It can't make a substantive change to the
> convention, just clarify it. If we can decide easily how to clarify it, that
> is fine. I'll amend the ticket if we have a clear decision. Otherwise, we
> should use a different ticket.
>
> Best wishes
>
> Jonathan
> _______________________________________________
> CF-metadata mailing list
> CF-metadata at cgd.ucar.edu
> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
I think we have a number of valid use cases for missing data in aux
coordinates, and i would vote to allow that.
Received on Wed Mar 28 2012 - 10:49:05 BST
