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calculate ELO

ed987
ed987 asked
on
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Last Modified: 2012-05-05
function k_elo($e)
{
  $eh=2400;$el=2000;
  $kh=16;$kl=32;

  if($e<$el)return $kl;
  if($e>$eh)return $kh;
  return ($eh-$e)*($kl-$kh)/($eh-$el)+$kh;
}
function calcELO(&$n1,&$n2,$won1,$canTie)
{
  $e1=$n1;
  $e2=$n2;
  $ea=1/(1+(float)pow(10,($e2-$e1)/400));
  $eb=1-$ea;

  $k1=k_elo($e1);
  $k2=k_elo($e2);
  if($won1==2)$sa=1;   //won
  if($won1==1)$sa=0.5; //even
  if($won1==0)$sa=0;   //lost
  $sb=1-$sa;

  $n1=round($e1+$k1*($sa-$ea),3);
  $n2=round($e2+$k2*($sb-$eb),3);
}

script above supposed to calculate ELO.
but it doesn't take information on previous games played !
how does one do that ?
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