Dear Jim
In Appendix A it does not say that the flag attributes are allowed for
coordinate variables - it has just "D" in the "Use" column. This is not an
argument why they shouldn't be if there is a need, but they weren't introduced
with that in mind. The use which you suggested for Martin's case is a good
idea, but I think it would need a change to the convention.
Best wishes
Jonathan
----- Forwarded message from Jim Biard <jbiard at cicsnc.org> -----
> Date: Wed, 12 Oct 2016 14:58:11 -0400
> From: Jim Biard <jbiard at cicsnc.org>
> To: cf-metadata at cgd.ucar.edu
> Subject: Re: [CF-metadata] Missing data bins in histograms
> User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:45.0)
> Gecko/20100101 Thunderbird/45.4.0
>
> Jonathan,
>
> Missing/fill values are not allowed, but I don't see any language
> prohibiting flags. I'd appreciate it if you could expand on your
> thoughts about why they aren't allowed.
>
> Grace and peace,
>
> Jim
> On 10/12/16 1:30 PM, Jonathan Gregory wrote:
> >Dear Jim
> >
> >That is an ingenious idea. I don't think the flag atts are currently allowed
> >for coord variables, but they could be, I agree.
> >
> >Best wishes
> >
> >Jonathan
> >
> >----- Forwarded message from Jim Biard <jbiard at cicsnc.org> -----
> >
> >>Date: Tue, 11 Oct 2016 14:39:56 -0400
> >>From: Jim Biard <jbiard at cicsnc.org>
> >>To: cf-metadata at cgd.ucar.edu
> >>Subject: Re: [CF-metadata] Missing data bins in histograms
> >>User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:45.0)
> >> Gecko/20100101 Thunderbird/45.4.0
> >>
> >>Hi.
> >>
> >>Another approach could be to use flag_values and flag_meanings on
> >>the coordinate variable to indicate one or more special coordinate
> >>values that correspond to any number of "missing data" or "out of
> >>bounds" bins. These attributes aren't forbidden by CF, and
> >>everything should be fine as long as the coordinate variable remains
> >>monotonic.
> >>
> >>Grace and peace,
> >>
> >>Jim
> >>
> >>On 10/11/16 8:41 AM, martin.juckes at stfc.ac.uk wrote:
> >>>Hello,
> >>>
> >>>the CF standard name list has two "histogram_.... " entries, and in the CMIP6 data request we may need to add a third, a histogram_of_cloud_top_height. Besides the standard name, we also need, for this new variable, a method of encoding the "missing data" bin in the histogram. That is, the histogram should record frequency in 16 data bins and one additional bin for the frequency of missing data.
> >>>
> >>>Can we define a "missing_data_index" attribute for histogram variables, and use this to indicate that the first bin in the array has this special purpose. It might be more pythonic to put the _FillValue in the coordinate value for the missing data bin, but I suspect that this would cause substantial problems for many software packages.
> >>>
> >>>regards,
> >>>Martin
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Received on Thu Oct 13 2016 - 03:42:47 BST
