#!/usr/bin/perl
# Simple linear fitting using the Least Squares method
# (c) 2003 Martin Mares <mj@ucw.cz>, GPL'ed

use strict;
use warnings;

my $n = 0;
my $sx = 0;
my $sy = 0;
my $sxy = 0;
my $sxx = 0;
my $syy = 0;
while (<STDIN>) {
	chomp;
	my ($x, $y) = split /\s+/;
	$n++;
	$sx += $x;
	$sy += $y;
	$sxy += $x * $y;
	$sxx += $x * $x;
	$syy += $y * $y;
}
$n || die "No data found";

my $b = ($n*$sxy - $sx*$sy) / ($n*$sxx - $sx*$sx);
my $a = ($sy - $sx*$b) / $n;
my $d = $syy - 2*$sy*$a - 2*$sxy*$b + $a*$a*$n + 2*$sx*$a*$b + $sxx*$b*$b;
my $var = $d / $n;
my $stdd = sqrt($var);

printf "Number of records:	%d\n", $n;
printf "a:			%.9f\n", $a;
printf "b:			%.9f\n", $b;
printf "1/b:			%.3f\n", 1/$b;
printf "Variance:		%.3f\n", $var;
printf "Std. deviation:		%.3f\n", $stdd;