Hello David,
I use mabs/mebs/mibs as shorthand, not as cell_methods.
I suggest, and NCO implements, cell_methods with the longer
versions that you prefer. The command line operators of NCO
accept either full or abbreviated versions (to save typing
when conducting the operation itself).
Now I see what you mean by the sentence in the appendix.
It could be read either way, and I read it the wrong way.
So I like your suggestion to clarify it.
Charlie
On 02/19/2015 04:27 PM, David Hassell wrote:
> Dear Charlie,
>
> I for one have no objection, in general, to new cell methods - I don't
> think that there are enough.
>
> Your suggestions (mabs/mibs/mebs) are clearly well defined, though I'm
> personally not so keen on the use of abbreviations. I've not seen
> these terms before, and wouldn't have guessed what they all mean. This
> is contrary to all of the other cell methods, which are unabbreviated
> and, I suspect, nearly universally understood.
>
> I dislike typing as much as anyone, but spelling them out is only 1 to
> 4 characters more than typing standard_deviation, the current longest
> method name:
>
> standard_deviation
> mean_absolute_value
> minimum_absolute_value
> maximum_absolute_value
>
> These terms seem nicely self describing to me. Do you think this is an
> option?
>
>> There appears to be an error in the draft 1.7 document. The sentence
>> describing Appendix E (the cell-methods appendix) says "In the Units
>> column, u indicates the units of the physical quantity before the
>> method is applied." Actually the units column entries are valid
>> _after_ the method is applied. Variance is the only method for which
>> this currently matters. This can be addressed independently of the
>> rest of the cell_methods suggestions proposed here.
>
> I think that this is OK. The column contains units after the method is
> applied, defined in terms of the original units ('u'). However, I
> agree that the terse description can mislead (as it did me just
> now!). How about replacing:
>
> "In the Units column, 'u' indicates the units of the physical
> quantity before the method is applied."
>
> with something like:
>
> "The Units column contains the units of the physical quantity after
> the method is applied, in terms of 'u', the units before the method
> is applied."
>
>
> All the best,
>
> David
>
>
> ---- Original message from Charlie Zender (11AM 19 Feb 15)
>
>> Date: Thu, 19 Feb 2015 11:56:22 -0800
>> From: Charlie Zender <zender at uci.edu>
>> To: CF Metadata Mail List <cf-metadata at cgd.ucar.edu>
>> Subject: [CF-metadata] New cell_methods: mabs/mibs/mebs?
>> User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:31.0)
>> Gecko/20100101 Thunderbird/31.4.0
>>
>> Dear CF-ers,
>>
>> The statistics mabs/mibs/mebs stand for "Maximum absolute value",
>> "Minimum absolute value", and "Mean absolute value", respectively.
>> They are similar to max/min/mean statistics, and they can be useful
>> in characterizing data when one wants positive-definite metrics.
>> mebs (unlike mean) does not allow positive and negative values to
>> compensate eachother. Unlike rms, mebs not does weight outliers
>> quadratically. NCO (version 4.4.8) implements mabs/mibs/mebs as
>> fundamental statistics (like max/min/mean/rms), and annotates the
>> cell_methods attribute of variables reduced by these statistics with
>> the strings "maximum_absolute_value", "minimum_absolute_value", and
>> "mean_absolute_value". I suggest CF adopt this, or some variant
>> pursuant to discussion.
>>
>> So I guess this is a request for discussion.
>> The relevant portions of CF are
>> http://cfconventions.org/Data/cf-conventions/cf-conventions-1.7/build/cf-conventions.html#cell-methods
>> http://cfconventions.org/Data/cf-conventions/cf-conventions-1.7/build/cf-conventions.html#appendix-cell-methods
>> The modifications that would be needed seem straightforward:
>> mention mabs/mebs/mibs in the text and then enlarge the existing
>> cell_methods table table by three rows.
>>
>> There appears to be an error in the draft 1.7 document. The sentence
>> describing Appendix E (the cell-methods appendix) says "In the Units
>> column, u indicates the units of the physical quantity before the
>> method is applied." Actually the units column entries are valid
>> _after_ the method is applied. Variance is the only method for which
>> this currently matters. This can be addressed independently
>> of the rest of the cell_methods suggestions proposed here.
>
> I think that this is OK. The column contains units after the method is
> applied, defined in terms of the original units ('u'). However, the
> terse description is misleading on first reading. How about something
> like:
>
> "In the Units column are the units of the physical quantity after the
> method is applied, in terms of 'u', the units before the method is
> applied."
>
>> Best,
>> Charlie
>> --
>> Charlie Zender, Earth System Sci. & Computer Sci.
>> University of California, Irvine 949-891-2429 )'(
>> _______________________________________________
>> CF-metadata mailing list
>> CF-metadata at cgd.ucar.edu
>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>
>
> --
> David Hassell
> National Centre for Atmospheric Science (NCAS)
> Department of Meteorology, University of Reading,
> Earley Gate, PO Box 243,
> Reading RG6 6BB, U.K.
>
> Tel : +44 118 3785613
> E-mail: d.c.hassell at reading.ac.uk
>
--
Charlie Zender, Earth System Sci. & Computer Sci.
University of California, Irvine 949-891-2429 )'(
Received on Thu Feb 19 2015 - 17:39:15 GMT
