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NOTICE: This version of the NSF Unidata web site (archive.unidata.ucar.edu) is no longer being updated.
Current content can be found at unidata.ucar.edu.
To learn about what's going on, see About the Archive Site.
Hi John, On Tue, 24 Apr 2001, John Caron wrote: > Davies, Harvey wrote: > > Firstly, I am having second thoughts about my suggested terms 'external' and > > 'internal'. A respected > > colleague thought they meant the opposite of what I meant. So how about > > just 'disk value' and 'memory value? > > Or 'physical value' and 'logical value'? > > Ive been using "external (packed)" and "internal (unpacked)". Does that > disambiguate it for your colleague? This seems reasonable. The User's Guide (UG) is consistent in using "external" to refer to data in a netCDF file. > > There are two cases. > > _FillValue is a valid value if it is within a valid range defined by > > valid_range, valid_min, valid_max. > > If none of these three attributes are defined then it is assumed that > > _FillValue is a missing value & > > should be used to define one end of the valid range. > > > > So if you want to use _FillValue to initialize a variable to a valid value > > 0, then you must define at > > least one of valid_range, valid_min, valid_max. > > this seems reasonable to me. Does anyone have datasets where this > algorithm would be wrong? A dataset that was written with a _FillValue within a specified valid range would not have that _FillValue treated as the valid default data value by many existing applications, i.e., such a dataset would break most existing applications. It's confusing to have _FillValue take on opposite meanings depending on whether or not a valid range is defined. I'd prefer that your interface didn't support this interpretation, especially since the UG recommends against it. Brian ----------------------------------------------------------------- Brian Eaton | email: eaton@xxxxxxxx Climate Modeling Section | National Center for Atmospheric Research | P.O. Box 3000, Boulder, CO 80307 |
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