Karl Taylor wrote:
> Hi all,
>
> I read in our convention that the missing_value is deprecated and
> should no longer be used (use _FillValue instead). What motivated the
> deprecation? It seems to me there is a fundamental difference between
> the two. My understanding is that the _FillValue is usually used by
> netCDF to prefill the disk space, so if the user fails to completely
> write all the arrays, but later tries to read in all elements, those
> elements unwritten will contain a predictable number (i.e., the
> _FillValue). It seems to me that incompletely writing data is in some
> sense a mistake, and this mistake can be easily identified by testing
> whether the _FillValue is found anywhere in the file. In the common
> climate modeling case, on the other hand, some data are "missing" not
> because we have made a mistake, but because some quantities are only
> calculated in certain regions (e.g., sea surface temperature is
> calculated only in ocean regions and is "missing" elsewhere).
>
> I think it is useful to distinguish between the different reasons for
> missing data. Because _FillValue is treated specially by netCDF, I
> think we should prefer the use of missing_value to identify data that
> have been written properly, but are missing by design.
>
> Tell me what danger there is in using a "deprecated" attribute in the
> writing of CF-compliant dataset. \
>
> thanks,
> Karl
>
> P.S. There is some urgency in addressing this issue since Jean-Yves
> Peterschmitt and I are writing a code that makes it easy to write
> CF-compliant output contributed to various model intercomparison
> projects and for IPCC contributions. Thanks for your thoughts.
>
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I just talked to Russ about this and we both agree with you, that
missing_value is useful for the reasons you state. (Note that valid_min,
valid_max, and valid_range are other standard attributes that can be
used for this).
We think that the NUG deprecation is out-of-data and should be, uh,
deprecated ;^}
Received on Wed Nov 05 2003 - 12:37:37 GMT
