Code Snippets for Simple Linear Regression Using Ruby Blog Post

denominator-snippet.rb

denominator = @xs.reduce(0) do |sum, x|
  sum + ((x - x_mean) ** 2)
end

full-slr-class-snippet.rb

class SimpleLinearRegression
  def initialize(xs, ys)
    @xs, @ys = xs, ys
    if @xs.length != @ys.length
      raise "Unbalanced data. xs need to be same length as ys"
    end
  end

  def y_intercept
    mean(@ys) - (slope * mean(@xs))
  end

  def slope
    x_mean = mean(@xs)
    y_mean = mean(@ys)

    numerator = (0...@xs.length).reduce(0) do |sum, i|
      sum + ((@xs[i] - x_mean) * (@ys[i] - y_mean))
    end

    denominator = @xs.reduce(0) do |sum, x|
      sum + ((x - x_mean) ** 2)
    end

    (numerator / denominator)
  end

  def mean(values)
    total = values.reduce(0) { |sum, x| x + sum }
    Float(total) / Float(values.length)
  end
end

numerator-snippet.rb

x_mean = mean(xs)
y_mean = mean(ys)

numerator = (0...@xs.length).reduce(0) do |sum, i|
  sum + ((@xs[i] - x_mean) * (@ys[i] - y_mean))
end

r-based-regression-snippet.R

data <- read.csv("path to csv")

lm(Number.of.Views ~ Days.Online, data = data)

run-regression-snippet.rb

require_relative 'simple-linear-regression'

data_file = File.open(ARGV[0])
data_file.readline # strip off the header

xs, ys = [], []

data_file.each do |line|
  x, y = line.split(",")
  xs << Float(x)
  ys << Float(y)
end

linear_model = SimpleLinearRegression.new(xs, ys)
puts "Model generated with"
puts "Slope: #{linear_model.slope}"
puts "Y-Intercept: #{linear_model.y_intercept}"
puts "\n"
puts "Estimated Linear Model:"
puts "Y = #{linear_model.y_intercept} + (#{linear_model.slope} * X)"

slr-blog-mean-snippet.rb

class SimpleLinearRegression
  def mean(values)
    total = values.reduce(0) { |sum, x| x + sum }
    Float(total) / Float(values.length)
  end
end

slr-class-with-slope-snippet.rb

class SimpleLinearRegression

  def initialize(xs, ys)
    @xs, @ys = xs, ys
    if @xs.length != @ys.length
      raise "Unbalanced data. xs need to be same length as ys"
    end
  end

  def slope
    x_mean = mean(@xs)
    y_mean = mean(@ys)

    numerator = (0...@xs.length).reduce(0) do |sum, i|
      sum + ((@xs[i] - x_mean) * (@ys[i] - y_mean))
    end

    denominator = @xs.reduce(0) do |sum, x|
      sum + ((x - x_mean) ** 2)
    end

    (numerator / denominator)
  end

  #Code truncated for clarity
end

y-intercept-snippet.rb

def y_intercept
  mean(@ys) - (slope * mean(@xs))
end