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#104: Clarify the interpretation of scalar coordinate variables
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  Reporter:  jonathan        |       Owner:  [email protected]
      Type:  defect          |      Status:  new                          
  Priority:  medium          |   Milestone:                               
 Component:  cf-conventions  |     Version:                               
Resolution:                  |    Keywords:                               
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Comment (by jonathan):

 Dear Nan

 Thank you for your comment. In the context of the whole paragraph, it is
 probably clearer than it appears when quoted by itself, but I agree it
 could be clarified further. Thanks for the suggestion. We could replace
 "character variable" in this sentence with "string-valued auxiliary
 coordinate variable". Is that OK?

 Here are the text changes we are now proposing, following Martin's and
 Nan's comments.

 '''Section 5.7, Scalar coordinate variables.'''

 Replace

   Under COARDS the method of providing a single valued coordinate was to
 add a dimension of size one to the variable, and supply the corresponding
 coordinate variable. The new scalar coordinate variable is a convenience
 feature which avoids adding size one dimensions to variables. Scalar
 coordinate variables have the same information content and can be used in
 the same contexts as a size one coordinate variable.

 with

   The use of scalar coordinate variables is a convenience feature which
 avoids adding size one dimensions to variables. A numeric scalar
 coordinate variable has the same information content and can be used in
 the same contexts as a size one numeric coordinate variable. Similarly, a
 string-valued scalar coordinate variable has the same meaning and purposes
 as a size one string-valued auxiliary coordinate variable (Section 6.1).

 At the end of the section, add:

   If a data variable has two or more scalar coordinate variables, they are
 regarded as though they were all independent coordinate variables with
 dimensions of size one. If two or more single-valued coordinates are not
 independent, but have related values (for instance, time and forecast
 period, or vertical coordinate and model level number, Section 6.2), they
 should be stored as coordinate or auxiliary coordinate variables of the
 same size one dimension, not as scalar coordinate variables.

 '''Section 6.1, Labels'''

 Replace the last sentence

   If a character variable has only one dimension (the maximum length of
 the string), it is regarded as a string-valued scalar coordinate variable,
 analogous to a numeric scalar coordinate variable (see Section 5.7, Scalar
 Coordinate Variables).

 with

   If a string-valued auxiliary coordinate variable has only one dimension
 (the maximum length of the string), it is a string-valued scalar
 coordinate variable (see Section 5.7, Scalar Coordinate Variables). As
 such, it has the same information content and can be used in the same
 contexts as a string-valued auxiliary coordinate variable of a size one
 dimension which has not been added to the data variable. This is a
 convenience feature.

 Cheers

 Jonathan

-- 
Ticket URL: <https://cf-pcmdi.llnl.gov/trac/ticket/104#comment:9>
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