Friendlier histogram.rb with automatic width and height

auto_histogram.rb

require 'histogram'

class AutoHistogram
  def initialize
    @values = []
  end

  def push(values)
    if values.kind_of? Numeric
      @values << values
    elsif values.respond_to? :each
      values.each { |value| push(value) }
    else
      raise "don't know how to push a #{values.class}"
    end
  end
  
  # Height and width are given in characters
  def report(height = nil, width = nil)
    terminal_height, terminal_width = *terminal_size
    
    height ||= terminal_height * 0.9 - 4
    width  ||= terminal_width  * 0.9
    
    max = @values.max
    min = @values.min
    
    # Expand bucket size so it feels 'natural' - meaning, it starts
    # with a 1, 2, or 5 and the rest is zeros
    min_bucket_size = (max - min) / height.to_f
    bucket_size = if min_bucket_size < 1
                    1
                  else
                    min_bucket_size_s = min_bucket_size.to_i.to_s
                    places = min_bucket_size_s.size - 1
                    first_digit = min_bucket_size_s.chars.first
                    prefix = case first_digit
                             when '1' then '2'
                             when '2', '3', '4' then '5'
                             when '5', '6', '7', '8', '9' then '10'
                             end
                    (prefix + '0' * places).to_i
                  end
    
    histogram = Histogram.new(min, max, bucket_size)
    @values.each { |v| histogram.push(v) }
    
    initial_width = histogram.to_s.split("\n").map(&:size).max
    width_scale = initial_width / width

    histogram.report(width_scale)
  end

  private

  def terminal_size
    %x{stty size}.split.collect { |x| x.to_i }
  end
end

if __FILE__ == $0
  # Example - requires histogram.rb from http://www.math.kobe-u.ac.jp/~kodama/tips-ruby-histogram.html

  h = AutoHistogram.new
  20000.times { h.push rand(100) + rand(100) + rand(100) }
  h.report
end