Seth-
Thanks very much for the information and pointer to the ticket
documenting the issue!
Do you know if NaN is an allowed value for actual_range? In our
historical data, a variable is retained if it was collected, even though
the sensor failed completely (and all the data was replaced by
_FillValue). In this case, actual_range would be [NaN NaN] for that
variable.
I appreciate the help!
Ellyn
On 05/22/2013 05:04 PM, Seth McGinnis wrote:
> Hi Ellyn,
>
> According to CF Trac Ticket #31 (slated for inclusion in the update to CF 1.7),
> the way to cache minimum & maximum values in metadata is to use an attribute
> named "actual_range" and store them as a pair.
>
> (I kind of think this is a bad idea, and wish that ticket was still open. I
> missed this discussion when it happened, but my experience with actual_max type
> attributes in practice has convinced me that it's SO easy for them to become
> inconsistent that it would really be better not to include them at all.
> Computing the min & max on the fly is cheap, and approximating it is even
> cheaper, so why introduce the uncertainty? But if they do need to go into
> metadata, I think it would be better to use a name that highlighted the fact
> that they're potentially unreliable. Maybe something like "nominal_range"
> rather than "actual_range"?)
>
> Anyway, the details on how actual_range works can be found here:
> https://cf-pcmdi.llnl.gov/trac/ticket/31
>
> Cheers,
>
> --Seth
>
>
>
>> The second part of the question involves variable attributes we now call
>> minimum and maximum. Do these names have special meanings? In our files, we
>> include the actual minimum and maximum computed for each non-coordinate
>> variable's data. I want to be clear about the content of these attributes,
>> and wonder if others use different terms to avoid confusion with valid_min and
>> valid_max? Would calling these attributes "computed_minimum" (maximum) or
>> "actual_minimum" (maximum) be better?
>>
>> Thanks for any suggestions!
>> Ellyn
--
Ellyn T. Montgomery, Oceanographer and Data Manager
U.S. Geological Survey
Woods Hole Coastal and Marine Science Center
384 Woods Hole Road, Woods Hole, MA 02543-1598
(508)457-2356
Received on Thu May 23 2013 - 06:43:51 BST
