Module: Babbage::Array

Defined in:
lib/babbage/array.rb

Class Method Summary collapse

Class Method Details

.average(array) ⇒ Object 



5
6
7
 
# File 'lib/babbage/array.rb', line 5

def self.average(array)
  sum(array).to_f / array.length
end

.maximum(array) ⇒ Object 



9
10
11
 
# File 'lib/babbage/array.rb', line 9

def self.maximum(array)
  array.max
end

.mean(array) ⇒ Object 



13
14
15
 
# File 'lib/babbage/array.rb', line 13

def self.mean(array)
  average(array)
end

.median(array) ⇒ Object 



17
18
19
 
# File 'lib/babbage/array.rb', line 17

def self.median(array)
  percentile(array, 50)
end

.minimum(array) ⇒ Object 



21
22
23
 
# File 'lib/babbage/array.rb', line 21

def self.minimum(array)
  array.min
end

.percentile(array, target) ⇒ Object 



25
26
27
28
29
30
31
32
33
34
35
36
 
# File 'lib/babbage/array.rb', line 25

def self.percentile(array, target)
  target = target.to_f / 100.0
  index = (array.length - 1) * target
  sorted_array = array.sort
  if index == index.to_i
    sorted_array[index.to_i]
  else
    average(
      sorted_array[index.floor, 2]
    )
  end
end

.root_mean_square_deviation(array, &estimator) ⇒ Object 



38
39
40
41
42
43
44
 
# File 'lib/babbage/array.rb', line 38

def self.root_mean_square_deviation(array, &estimator)
  Math.sqrt(
    average(
      array.map(&estimator)
    )
  )
end

.standard_deviation(array) ⇒ Object 



46
47
48
49
50
51
 
# File 'lib/babbage/array.rb', line 46

def self.standard_deviation(array)
  avg = average(array)
  root_mean_square_deviation(array) do |value|
    (value - avg) ** 2
  end
end

.sum(array) ⇒ Object 



53
54
55
 
# File 'lib/babbage/array.rb', line 53

def self.sum(array)
  array.inject(0) {|sum,value| sum + value}
end

.variance(array) ⇒ Object 



57
58
59
60
61
62
 
# File 'lib/babbage/array.rb', line 57

def self.variance(array)
  avg = average(array)
  average(
    array.map {|value| (value - avg) ** 2 }
  )
end