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.
Best,
Charlie
--
Charlie Zender, Earth System Sci. & Computer Sci.
University of California, Irvine 949-891-2429 )'(
Received on Thu Feb 19 2015 - 12:56:22 GMT
