Module: Enumerable

Defined in:
lib/terragona/stats.rb

Overview

Taken from: stackoverflow.com/questions/7749568/how-can-i-do-standard-deviation-in-ruby

Instance Method Summary collapse

Instance Method Details

#mean ⇒ Object 



10
11
12
13
 
# File 'lib/terragona/stats.rb', line 10

def mean
  return if self.empty?
  return self.sum / self.length.to_f
end

#sample_variance ⇒ Object 



15
16
17
18
19
 
# File 'lib/terragona/stats.rb', line 15

def sample_variance
  m = self.mean
  sum = self.inject(0){|accum, i| accum + (i - m) ** 2 }
  return sum / (self.length - 1).to_f
end

#standard_deviation ⇒ Object 



21
22
23
 
# File 'lib/terragona/stats.rb', line 21

def standard_deviation
  return Math.sqrt(self.sample_variance)
end

#sum ⇒ Object 



6
7
8
 
# File 'lib/terragona/stats.rb', line 6

def sum
  return self.inject(0){|accum, i| accum + i }
end