[eml-dev] annotating log-transformed units

[Carl Boettiger]

Yes, I agree entirely that it would be nice if researchers always defined a
reference length; e.g. jaw length as a fraction of body length, etc, and
then the units are pure and it makes sense to take a logarithm.

I suppose that's the role the standard unit plays when researchers measure
a bunch of values in some unit (e.g. cm) and then take the logarithm, we
can think of this as a dimensionless value: length(measured)/length(cm).
 But this begs the question of how we denote the reference unit
(denominator).  I can add it to the column metadata (attributeDiscription)
in plain text, but it seems a better solution would provide a more
machine-readable way to, e.g. recover the initial lengths.

Thanks for the feedback and suggestions.


On Tue, Nov 26, 2013 at 10:08 AM, Matt Jones <jones at nceas.ucsb.edu> wrote:

> I think that both the input to and output of the log function are
> dimensionless numbers.  So I would use dimensionless in my EML unit. See
> these discussions:
>
>
> http://physics.stackexchange.com/questions/13060/what-is-the-logarithm-of-a-kilometer-is-it-a-dimensionless-number
>
> http://www.sciforums.com/showthread.php?64346-what-s-the-UNIT-after-you-take-the-natural-log
>
> Matt
>
>
> On Tue, Nov 26, 2013 at 6:34 AM, Carl Boettiger <cboettig at gmail.com>wrote:
>
>> Hi eml-dev,
>>
>> Any advice on the best way to write the EML attribute metadata for, e.g.
>> a column whose units are log-transformed lengths measured in centimeters?
>> (Logarithms being 'pure', formally).  (I see definitions for powers but not
>> logs among the standardUnits<http://knb.ecoinformatics.org/software/eml/eml-2.1.1/eml-unitTypeDefinitions.html>)
>>
>>
>> Would this require a custom unit definition?  Seems like this might be a
>> reasonably common use-case, so curious how others are handling it.
>>
>> Thanks and sorry for the bother,
>>
>> - Carl
>>
>> (referred from reml/issues/57<https://github.com/ropensci/reml/issues/57>
>> )
>>
>> --
>> Carl Boettiger
>> UC Santa Cruz
>> http://carlboettiger.info/
>>
>> _______________________________________________
>> Eml-dev mailing list
>> Eml-dev at ecoinformatics.org
>> http://lists.nceas.ucsb.edu/ecoinformatics/mailman/listinfo/eml-dev
>>
>>
>


-- 
Carl Boettiger
UC Santa Cruz
http://carlboettiger.info/
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