#! /usr/bin/env python

## to run and view the results, do this:
## $ python lsq.py > lin-out
## $ gnuplot
## gnuplot> plot 'linear.dat' with linespoints
## gnuplot> replot 'lin-out' with linespoints


import string

def __main__():

  sum_x = 0
  sum_x2 = 0
  sum_y = 0
  sum_xy = 0
  N = 0
  
  lines = open('linear.dat').readlines()
  for line in lines:
    fwords = map(float, string.split(line))
    sum_x += fwords[0]
    sum_y += fwords[1]
    sum_x2 += fwords[0]*fwords[0]
    sum_xy += fwords[0]*fwords[1]
    N += 1
  m = (sum_y*sum_x/N - sum_xy)/(sum_x*sum_x/N - sum_x2)
  b = (sum_y - m*sum_x)/N
  print '## line equation is y = m * x + b =', m, '* x + (', b, ')'
  for i in range(120):
    x = i/5.0
    print x, m*x + b

__main__()