Ruby Native Statistics

This is a native extension to Ruby that adds native (C) statistical functions to the Array class. At present the following functions are provided:

• Sample Standard Deviation (stdev, stdevs)
• Population Standard Deviation (stdevp)
• Sample Variance (var)
• Population Variance (varp)
• Median (median)
• Mean (mean)
• Percentile (percentile)

Check the Github Actions build to see the currently supported versions of Ruby. This list will match whatever stable versions are specified at https://www.ruby-lang.org/en/downloads/.

It is generally more performant than calculating these values with pure Ruby. For a comparison, run the benchmarks with rake benchmark.

If you found a bug or need a particular function, please let me know! I work on this gem in my spare time, mainly for learning purposes. Feel free to open a PR or a Github issue and I'll take a look as soon as possible.

require 'ruby_native_statistics'
r = [1,3,21,32,42]

# calculate sample standard deviation, you can also use "stdevs"
p r.stdev

# calculate population standard deviation
p r.stdevp

# calculate mean
p r.mean

# calculate median
p r.median

# calculate percentile
p r.percentile(0.3333)

Percentile uses the same rounding method as Excel, sometimes called R7.

This is the third version of this gem, and it is a total rewrite of a SWIG-based design. Lots of thanks to the following resources:

• https://blog.jcoglan.com/2012/07/29/your-first-ruby-native-extension-c/
• https://github.com/andremedeiros/ruby-c-cheat-sheet
• http://silverhammermba.github.io/emberb/c/
• http://docs.ruby-lang.org/en/2.3.0/extension_rdoc.html