Expose the two possible standard deviations as separate visitors and functions
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Key: GEOT-3329
URL: http://jira.codehaus.org/browse/GEOT-3329
Project: GeoTools
Issue Type: Improvement
Components: core main, data jdbc-ng
Affects Versions: 2.7-M3
Reporter: Andrea Aime
Assignee: Andrea Aime
Fix For: 2.7-M4
The standard deviation is unfortunately not defined as one function, but two,
sample and population (aka biased):
http://en.wikipedia.org/wiki/Standard_deviation
http://mathworld.wolfram.com/StandardDeviation.html
One divides the variance by N, the other by N-1.
The GeoTools StandardDeviation function uses division by N, most databases (but
not all) use N-1 instead when stddev is called.
Have Geotools do like various databases, that recently exposed two separate
functions to avoid the confusion:
http://www.postgresql.org/docs/8.4/interactive/functions-aggregate.html
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