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 <[email protected]> > To: [email protected] > 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 <[email protected]> ----- > > > Date: Tue, 16 Feb 2016 16:05:57 -0800 > > From: Charlie Zender <[email protected]> > > To: David Hassell <[email protected]> > > CC: CF Metadata Mail List <[email protected]> > > 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 <[email protected]> > > >>To: David Hassell <[email protected]> > > >>CC: CF Metadata Mail List <[email protected]> > > >>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 <[email protected]> > > >>>>To: CF Metadata Mail List <[email protected]> > > >>>>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 > > >>>>[email protected] > > >>>>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: [email protected] > > >>> > > >> > > >>-- > > >>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: [email protected] > > > > > > > -- > > Charlie Zender, Earth System Sci. & Computer Sci. > > University of California, Irvine 949-891-2429 )'( > > _______________________________________________ > > CF-metadata mailing list > > [email protected] > > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > > ----- End forwarded message ----- > _______________________________________________ > CF-metadata mailing list > [email protected] > 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: [email protected] _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
