Dear Charlie
I don't remember this discussion. Perhaps I commented it at the time! Anyway,
I think the three you proposed before are well-defined and suitable for
proposal in CF if you know of actual use-cases for them - do you? To propose
a modification to the convention, please open a trac ticket.
I'm not sure about
> sum_absolute_value u The data values are representative of
> a sum or accumulation of the absolute values over the cell.
I can see what you mean, but I can't think of a practical example of it.
What is the use-case?
Best wishes
Jonathan
----- Forwarded message from Charlie Zender <zender at uci.edu> -----
> Date: Tue, 16 Feb 2016 16:05:57 -0800
> From: Charlie Zender <zender at uci.edu>
> To: David Hassell <d.c.hassell at reading.ac.uk>
> CC: CF Metadata Mail List <cf-metadata at cgd.ucar.edu>
> Subject: Re: [CF-metadata] New cell_methods: mabs/mibs/mebs?
> User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:38.0)
> Gecko/20100101 Thunderbird/38.5.1
>
> Dear CFers,
>
> About a year ago I proposed three new cell-methods (mibs/mabs/mebs).
> The proposal received some discussion, and what I infer from silence
> as acquiescence. To those three methods I now propose adding a fourth:
> tabs = total absolute value whose CF mehod would be encoded as
> sum_absolute_value (or, if people prefer, total_absolute_value).
> tabs is analogous to the existing "sum" statistic but is computed
> with absolute values. Its utility is in computing statistics of
> quantities whose magnitude not signedness is the key metric. Its
> omission in my original proposal was an oversight.
>
> The full set of recommendations could be implemented in CF by
> inserting the following line into Table E.1. Cell Methods
>
> http://cfconventions.org/Data/cf-conventions/cf-conventions-1.7/build/cf-conventions.html#appendix-cell-methods
>
> cell_methods: Units: Description
> maximum_absolute_value u Maximum absolute value
> minimum_absolute_value u Minimum absolute value
> mean_absolute_value u Mean absolute value
> sum_absolute_value u The data values are representative of
> a sum or accumulation of the absolute values over the cell.
>
> Thoughts?
>
> Best,
> Charlie
>
> On 2/20/15 00:55, David Hassell wrote:
> >Hi Charlie,
> >
> >>the strings "maximum_absolute_value", "minimum_absolute_value",
> >>and "mean_absolute_value". I suggest CF adopt this, or some
> >>variant pursuant to discussion.
> >
> >Many apologies - for some reason, I failed to register this crucial
> >sentence when I replied. I suppose that it's good that the same names
> >were arrived at without prior knowledge.
> >
> >No objections from me, then.
> >
> >All the best,
> >
> >David
> >
> >---- Original message from Charlie Zender (04PM 19 Feb 15)
> >
> >>Date: Thu, 19 Feb 2015 16:39:15 -0800
> >>From: Charlie Zender <zender at uci.edu>
> >>To: David Hassell <d.c.hassell at reading.ac.uk>
> >>CC: CF Metadata Mail List <cf-metadata at cgd.ucar.edu>
> >>Subject: Re: [CF-metadata] New cell_methods: mabs/mibs/mebs?
> >>User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101
> >> Thunderbird/31.4.0
> >>
> >>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 )'(
> >
> >
> >--
> >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 )'(
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> CF-metadata at cgd.ucar.edu
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----- End forwarded message -----
Received on Wed Feb 17 2016 - 07:00:31 GMT
