> So adding actual_min/max as recommended attributes should help users
> from mistakenly using valid min/max.
Yes, I agree. I've seen this problem lots of times too. I think in
general it's quite hard to decide what to put in valid_min and
valid_max so people just (incorrectly) use the actual min/max.
Jon
On Tue, Jun 10, 2008 at 12:53 AM, John Caron <caron at unidata.ucar.edu> wrote:
> I also like "actual_min" and "actual_max": short and to the point.
>
> One point Ill make is that I see a number of well thought out files
> using valid_min and valid_max when they really mean actual_min and
> actual_max. On first glance this may seem harmless, but it triggers (in
> the netcdf-java library default behavior) a costly scan of the data
> looking for invalid data, ie values outside that range.
>
> So adding actual_min/max as recommended attributes should help users
> from mistakenly using valid min/max. And its very useful for visualizers
> to create color scales etc.
>
> Julia Collins wrote:
>> On Mon, 9 Jun 2008, Jon Blower wrote:
>>
>>> I have rediscovered this conversation in the depths of my inbox and
>>> thought it might be worth resurrecting. To summarize the discussion
>>> so far:
>>> 1) I proposed two new standard optional CF attributes (called
>>> something like minimum_data_value and maximum_data_value) that would
>>> be attached to a variable in a NetCDF file, redundantly holding its
>>> actual min and max values in that file. [...] As well as helping with data
>>> mining applications, this would act as a hint to visualization
>>> packages to provide a first attempt at automatically defining a colour
>>> scale range for sensible portrayal. Note that this attribute pair is
>>> distinct in purpose from valid_min and valid_max (which contains
>>> theoretical extrema, beyond which data is considered invalid).
>>>
>>
>> I support the idea of formalizing these sorts of attributes in some
>> way. However, I would prefer a simpler name(s). For example: "actual_min"
>> and "actual_max." Less typing :-), and more like the existing "valid_min"
>> and "valid_max" attributes.
>>
>> Julia
>> --
>> Julia Collins
>> National Snow and Ice Data Center
>> CIRES, University of Colorado, Boulder
>> 449 UCB
>> Boulder, CO 80309-0449
>> Voice: 303-492-6405
>> E-mail: collinsj at nsidc.org
>> _______________________________________________
>> CF-metadata mailing list
>> CF-metadata at cgd.ucar.edu
>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>>
> _______________________________________________
> CF-metadata mailing list
> CF-metadata at cgd.ucar.edu
> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>
--
--------------------------------------------------------------
Dr Jon Blower Tel: +44 118 378 5213 (direct line)
Technical Director Tel: +44 118 378 8741 (ESSC)
Reading e-Science Centre Fax: +44 118 378 6413
ESSC Email: jdb at mail.nerc-essc.ac.uk
University of Reading
3 Earley Gate
Reading RG6 6AL, UK
--------------------------------------------------------------
Received on Tue Jun 10 2008 - 00:24:23 BST
