Class: DRbDump::Statistic

Inherits:
Object
  • Object
show all
Defined in:
lib/drbdump/statistic.rb

Overview

Stores the minimum, maximum, mean, count and standard deviation for a set of values but not the values themselves.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Statistic

:nodoc:



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# File 'lib/drbdump/statistic.rb', line 27

def initialize # :nodoc:
  @M_2   = 0.0
  @count = 0
  @max   = -Float::INFINITY
  @mean  = 0.0
  @min   = Float::INFINITY
end

Instance Attribute Details

#count ⇒ Object (readonly)

The number of items in the set



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# File 'lib/drbdump/statistic.rb', line 10

def count
  @count
end

#max ⇒ Object (readonly) Also known as: maximum

The maximum value added



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# File 'lib/drbdump/statistic.rb', line 15

def max
  @max
end

#mean ⇒ Object (readonly) Also known as: average

The mean of all values



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# File 'lib/drbdump/statistic.rb', line 20

def mean
  @mean
end

#min ⇒ Object (readonly) Also known as: minimum

The minimum value added



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# File 'lib/drbdump/statistic.rb', line 25

def min
  @min
end

Instance Method Details

#add(value) ⇒ Object

Adds value to the set of values. Returns the number of values.



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# File 'lib/drbdump/statistic.rb', line 38

def add value
  @min = value if value < @min
  @max = value if value > @max
  @count += 1

  delta  = value - @mean
  @mean += delta / @count
  @M_2  += delta * (value - @mean)

  @count
end

#sample_variance ⇒ Object

The sample variance for all values



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# File 'lib/drbdump/statistic.rb', line 68

def sample_variance
  sv = @M_2 / (@count - 1)
  return 0.0 if sv.nan?
  sv
end

#standard_deviation ⇒ Object

The standard deviation of all values



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# File 'lib/drbdump/statistic.rb', line 77

def standard_deviation
  Math.sqrt sample_variance
end

#to_a ⇒ Object

An array containing the number of values in the set, the mean and the standard deviation



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# File 'lib/drbdump/statistic.rb', line 85

def to_a
  [@count, @min, @mean, @max, standard_deviation]
end