use strict;
use Statistics::Regression;

my $reg= Statistics::Regression->new( 3, "quad regression", [ "const", "X", "X^2" ] );
              
my @array = ('62.6',	'62.8',	'63',	'63.3',	'63.5',	'63.7',	'64');
my @array2 = ('7.476',	'7.5219', '7.5464', '7.5516', '7.5504',	'7.5372', '7.518');
my $i;
for $i (0..$#array) {
   my $x = $array[$i];
   my $x2 = $x * $x;
   my $y = $array2[$i];
   $reg->include($y, [1.0, $x, $x2]);
}
              
my $theta = $reg->theta();
print "Coefficients: ",join(",",@$theta),"\n";
my $c = $theta->[0];
my $b = $theta->[1];
my $a = $theta->[2];

print "\nComputed results:\n";
for $i (0..$#array) {
   my $x = $array[$i];
   my $y = ($a*$x + $b)*$x + $c;
   my $ytrue = $array2[$i];
   print "$x\t$y\t($ytrue)\n";
}

# Solve for the derivative being 0.
my $maxx = -$b/(2.0*$a);
my $maxy = ($a*$maxx + $b)*$maxx + $c;
print "\nPeak point:\n";
print "$maxx\t$maxy\n";