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Thank you Jim!
When we transition our older files to CF, I'll have to leave out
the variables for which there is no good data.
Best, Ellyn
On 05/23/2013 08:49 AM, Jim Biard wrote:
Ellyn,
I believe that the valid_range and actual_range attributes
are intended to only list non-fill values. The actual range
should fall inside the valid range, and both should exclude
invalid values.
Grace and peace,
Jim
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
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--
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
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