Adds standard deviation methods to ActiveRecord. sqlite does not include standard deviation methods by default, so this is designed for mysql only.
./script/plugin install git://github.com/jmckible/standard_deviation.git
This plugin adds two new aggregations methods to ActiveRecord: std and variance. Say you’ve got a measurements table with an integer column called ‘integer.’
Measurement.std(:integer) # => 0.8165 Measurement.variance(:integer) # => 0.6667
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standard_deviation was created by Jordan McKible jordan.mckible.com
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Available on GitHub at github.com/jmckible/standard_deviation