Module: Nuggets::Array::HistogramMixin

Included in:
Array
Defined in:
lib/nuggets/array/histogram_mixin.rb

Defined Under Namespace

Classes: HistogramItem

Constant Summary collapse

FORMATS =

Provides some default formats for #formatted_histogram.

Example:

(default)         ab  [==]  2
(percent)         xyz [===] 3 (37.50%)
(numeric)          42 [==]  2
(numeric_percent) 123 [=]   1 (12.50%)

The “numeric” variants format the item as a (decimal) number.

{
  :default         => '%-*s [%s]%*s %*d',
  :percent         => '%-*s [%s]%*s %*d (%.2f%%)',
  :numeric         =>  '%*d [%s]%*s %*d',
  :numeric_percent =>  '%*d [%s]%*s %*d (%.2f%%)'
}

Instance Method Summary collapse

Instance Method Details

#annotated_histogram ⇒ Object

call-seq:

array.annotated_histogram => anArray
array.annotated_histogram { |hist_item| ... } => aHash

Calculates the #histogram for array and yields each histogram item (see HistogramItem) to the block or returns an Array of the histogram items.



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# File 'lib/nuggets/array/histogram_mixin.rb', line 96

def annotated_histogram
  hist, items = histogram, []

  percentage = size / 100.0

  max_freq = hist.values.max
  max_freq_length = max_freq.to_s.length

  max_item_length = hist.keys.map { |item| item.to_s.length }.max

  # try to sort the histogram hash
  begin
    hist = hist.sort
  rescue ::ArgumentError
  end

  hist.each { |item, freq|
    hist_item = HistogramItem.new(
      item, freq, max_freq, max_freq_length, max_item_length, freq / percentage
    )

    block_given? ? yield(hist_item) : items << hist_item
  }

  block_given? ? hist : items
end

#formatted_histogram(format = :default, indicator = '=') ⇒ Object

call-seq:

array.formatted_histogram([format[, indicator]]) => aString

Returns the #histogram of array as a formatted String according to format, using indicator to draw the frequency bar.

format may be a Symbol indicating one of the provided default formats (see FORMATS) or a format String (see Kernel#sprintf) that will receive the following arguments (in order):

  1. max_item_length (Integer)

  2. item (String)

  3. “frequency_bar” (String)

  4. “padding” (String)

  5. max_freq_length (Integer)

  6. freq (Integer)

  7. percentage (Float, optional)

See HistogramItem for further details on the individual arguments.

Raises:

  • (::TypeError) 


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# File 'lib/nuggets/array/histogram_mixin.rb', line 142

def formatted_histogram(format = :default, indicator = '=')
  format = FORMATS[format] if FORMATS.key?(format)
  raise ::TypeError, "String expected, got #{format.class}" unless format.is_a?(::String)

  include_percentage = format.include?('%%')
  indicator_length   = indicator.length

  lines = []

  annotated_histogram { |hist|
    arguments = [
      hist.max_item_length, hist.item,                     # item (padded)
      indicator * hist.freq,                               # indicator bar
      (hist.max_freq - hist.freq) * indicator_length, '',  # indicator padding
      hist.max_freq_length, hist.freq                      # frequency (padded)
    ]

    arguments << hist.percentage if include_percentage     # percentage (optional)

    lines << format % arguments
  }

  lines.join("\n")
end

#histogram ⇒ Object

call-seq:

array.histogram => aHash
array.histogram { |x| ... } => aHash

Calculates the frequency histogram of the values in array. Returns a Hash that maps any value, or the result of the value yielded to the block, to its frequency.



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# File 'lib/nuggets/array/histogram_mixin.rb', line 68

def histogram
  hist = ::Hash.new(0)
  each { |x| hist[block_given? ? yield(x) : x] += 1 }
  hist
end

#probability_mass_function(&block) ⇒ Object Also known as: pmf

call-seq:

array.probability_mass_function => aHash
array.probability_mass_function { |x| ... } => aHash

Calculates the probability mass function (normalized histogram) of the values in array. Returns a Hash that maps any value, or the result of the value yielded to the block, to its probability (via #histogram).



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# File 'lib/nuggets/array/histogram_mixin.rb', line 82

def probability_mass_function(&block)
  hist, n = histogram(&block), size.to_f
  hist.each { |k, v| hist[k] = v / n }
end