Class: LEWT::MetaMath

Inherits:
Object
  • Object
show all
Defined in:
lib/extensions/metastat/metamath.rb

Overview

MetaMath is a base class for developing statistics routines for use with the Metastat LEWT extension It provides some convienience methods for developing new routines, as well as acting as a container for common mathematical proceedures.

Direct Known Subclasses

PearsonR, SimpleRegression

Instance Method Summary collapse

Instance Method Details

#descriptive_stats(ar) ⇒ Object

Return the descriptive statistics for an array of values [mean, media, mode]

ar

Array of values



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# File 'lib/extensions/metastat/metamath.rb', line 41

def descriptive_stats(ar)
  raise TypeError "Expected an array" if not ar.kind_of?(Array)
  return {
    :mean => mean(ar),
    :median => median(ar),
    :mode => mode(ar)
  }
end

#mean(ar) ⇒ Object

Takes an array of numeric values and returns there mean.

ar

Array of values



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# File 'lib/extensions/metastat/metamath.rb', line 17

def mean(ar)
  raise TypeError "Expected an array" if not ar.kind_of?(Array)
  total = ar.reduce(0) { |sum, x| x + sum }
  return Float(total)/Float(ar.length)
end

#median(ar) ⇒ Object

Takes an array of values and returns the median

ar

Array of values



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# File 'lib/extensions/metastat/metamath.rb', line 33

def median(ar)
  raise TypeError "Expected an array" if not ar.kind_of?(Array)
  mid = ar.length / 2
  return (mid % 1 != 0) ? mean( [ ar[(mid).floor], ar[(mid).round ]] ) : ar[mid]
end

#mode(ar) ⇒ Object

Takes an array of values and returns there mode.

ar

Array of values



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# File 'lib/extensions/metastat/metamath.rb', line 25

def mode(ar)
  raise TypeError "Expected an array" if not ar.kind_of?(Array)
  freq = ar.inject(Hash.new(0)) { |h,v| h[v] += 1; h }
  return ar.max_by { |v| freq[v] }
end