Class: Mean

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

Overview

Allows calculation of arithmetic, geometric and harmonic means. Class methods allow the passing in of a data set. Alternatively an object can be created and elements can be added with #push

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(params = {}) ⇒ Mean

Remember the initial state.

If you are passing in an initial state:

arithmetic mean

needs ‘:sum` and `:count`

geometric mean

needs ‘:product` and `:count`

harmonic mean

needs ‘:sum_of_reciprocals` and `:count`

Parameters:

  • (Hash{Symbol => Numeric})

Raises:

  • if ‘:count` is negative

  • if ‘:sum_of_reciprocals` is negative

  • if ‘:product` is negative



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# File 'lib/means.rb', line 41

def initialize(params={})
  check_params params
  assign_defaults params
end

Class Method Details

.arithmetic(data) ⇒ Numeric?

Calculate the arithmetic mean

Parameters:

  • data (Array<Numeric>) —

    the data values

Returns:

  • (Numeric, nil) —

    the arithmetic mean or nil if there is no data



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# File 'lib/means.rb', line 13

def Mean.arithmetic(data)
  data.sum / data.size unless data.empty?
end

.geometric(data) ⇒ Numeric?

Calculate the geometric mean

Parameters:

  • data (Array<Numeric>) —

    the data values

Returns:

  • (Numeric, nil) —

    the geometric mean or nil if there is no data or any elements are zero or negative



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# File 'lib/means.rb', line 20

def Mean.geometric(data)
  data.reduce(:*) ** (1 / data.size) unless data.empty? or includes_zero_or_negative? data
end

.harmonic(data) ⇒ Numeric?

Calculate the harmonic mean

Parameters:

  • data (Array<Numeric>) —

    the data values

Returns:

  • (Numeric, nil) —

    the harmonic mean or nil if there is no data or any elements are zero or negative



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# File 'lib/means.rb', line 27

def Mean.harmonic(data)
  data.size / data.reduce(0) {|sum, element| sum += (1 / element)} unless data.empty? or includes_zero_or_negative? data
end

Instance Method Details

#arithmetic_mean ⇒ Numeric?

Calculate the arithmetic mean

Returns:

  • (Numeric, nil) —

    the arithmetic mean or nil if there is no data



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# File 'lib/means.rb', line 62

def arithmetic_mean
  @sum / @count unless @count.zero?
end

#geometric_mean ⇒ Numeric?

Calculate the geometric mean

Returns:

  • (Numeric, nil) —

    the geometric mean or nil if there is no data or any elements are zero or negative



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# File 'lib/means.rb', line 68

def geometric_mean
  @product ** (1 / @count) unless @count.zero? or @includes_zero_or_negative
end

#harmonic_mean ⇒ Numeric?

Calculate the harmonic mean

Returns:

  • (Numeric, nil) —

    the harmonic mean or nil if there is no data or any elements are zero or negative



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# File 'lib/means.rb', line 74

def harmonic_mean
  @count / @sum_of_reciprocals unless @count.zero? or @includes_zero_or_negative
end

#push(element) ⇒ Object

Add element to the data set

Parameters:

  • element (Numeric) —

    the element to add



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# File 'lib/means.rb', line 48

def push(element)
  @includes_zero_or_negative = true if Mean.zero_or_negative? element

  unless @includes_zero_or_negative
    @sum_of_reciprocals += (1 / element)
    @product *= element
  end

  @sum += element
  @count += 1
end