Hi Charlie,
I liked your propsal back then, and still do. I will happily moderate
a trac ticket if you want to open one.
All the best,
David
---- Original message from Jonathan Gregory (02PM 17 Feb 16)
> Date: Wed, 17 Feb 2016 14:00:31 +0000
> From: Jonathan Gregory <j.m.gregory at reading.ac.uk>
> To: cf-metadata at cgd.ucar.edu
> Subject: Re: [CF-metadata] New cell_methods: mabs/mibs/mebs?
> User-Agent: Mutt/1.5.21 (2010-09-15)
>
> 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 )'(
> > _______________________________________________
> > CF-metadata mailing list
> > CF-metadata at cgd.ucar.edu
> > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>
> ----- End forwarded message -----
> _______________________________________________
> 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
Received on Wed Feb 17 2016 - 07:07:15 GMT
