Class: Array

Inherits:
Object
  • Object
show all
Defined in:
lib/crunchr/active_record.rb,
lib/crunchr/core_ext.rb

Overview

stuff for dealing with statistics

monkey patches Hash, Array, ActiveRecord::Base and ActiveRecord::Relation

Instance Method Summary collapse

Instance Method Details

#mean ⇒ Object 



30
31
32
 
# File 'lib/crunchr/core_ext.rb', line 30

def mean
  (self.sum * 1.0) / self.count
end

#median ⇒ Object 



38
39
40
41
42
43
44
45
 
# File 'lib/crunchr/core_ext.rb', line 38

def median
  center = (self.count + (self.count % 2)) / 2
  list = self.sort

  self.count % 2 == 0 ?
   [ list[center - 1], list[center] ].mean :
   list[center - 1]
end

#mode ⇒ Object 



52
53
54
55
56
 
# File 'lib/crunchr/core_ext.rb', line 52

def mode
  counts = {}
  self.collect { |i| counts[i] ||= 0; counts[i] += 1 }
  counts.key(counts.values.sort.last)
end

#range ⇒ Object 



47
48
49
50
 
# File 'lib/crunchr/core_ext.rb', line 47

def range
  list = self.sort
  list.last - list.first
end

#stddev ⇒ Object 



34
35
36
 
# File 'lib/crunchr/core_ext.rb', line 34

def stddev
  Math.sqrt(self.collect{ |i| (i - self.mean) ** 2 }.sum) / Math.sqrt(self.count - 1)
end

#sum ⇒ Object 



26
27
28
 
# File 'lib/crunchr/core_ext.rb', line 26

def sum
  self.inject(0.0) { |s, i| (s += i) rescue s }
end

#timed_interval(length, amount = 1) ⇒ Object

return an array of arrays where each inner array represents a period of time

Synopsis

timed_interval(:week, 2)   # two week periods
timed_interval(:month, 6)  # half year periods
timed_interval(:day, 1)    # per day

Prerequisites

The items in the list must respond_to interval_time and it must return something that responds to < or >



19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
 
# File 'lib/crunchr/active_record.rb', line 19

def timed_interval(length, amount=1)
  list = self.sort_by(&:created_at)
  current = list.first.interval_time(length)


  records = []
  period  = []

  list.each do |record|
    if record.interval_time(length) > (current + (amount - 1))
      records << period
      period = []
      current = record.interval_time(length)
    end

    period << record
  end

  records
end