data = File.read('data.csv').split("\n").map { |d| d.split(',').map(&:to_f) }
iterations = 1000
m = data.size
alpha = 0.0001
theta0 = 0
theta1 = 0

(1..iterations).each do |iter|
  d_theta0 = 0
  d_theta1 = 0
  (0..(m - 1)).each do |i|
    x = data[i][0]
    y = data[i][1]
    d_theta0 += (y - (theta1 * x + theta0))
    d_theta1 += (y - (theta1 * x + theta0)) * x
  end
  theta0 = theta0 + alpha * d_theta0
  theta1 = theta1 + alpha * d_theta1
  puts "#{iter}: f(x) = #{theta1} * x + #{theta0}"
end

puts "f(x) = #{theta1} * x + #{theta0}"