<!-- Author: Brian Mackenzie -->
<!-- Date: 1 December 2007 -->
<!-- Version: 1.0 -->

function lungcalc()
{
var age = document.lung.age.value;
var height = document.lung.height.value;
var gender = document.lung.gender.options[document.lung.gender.selectedIndex].value;

  if (gender == "female")
    {
		fvc = (0.0414 * height) - (0.0232 * age) - 2.2;
		fev = (0.0268 * height) - (0.0251 * age) - 0.38;
		fevfc = (fev / fvc) * 100;
		mmv = 40 * fev;		
    }

  if (gender == "male")
    {
		fvc = (0.0774 * height) - (0.0212 * age) - 7.75;
		fev = (0.0566 * height) - (0.0233 * age) - 4.91;
		fevfc = (fev / fvc) * 100;
		mmv = 40 * fev;		
    }

  document.lung.fvc.value = nt2dp(fvc,1);
  document.lung.fev.value = nt2dp(fev,1);
  document.lung.fevfc.value = nt2dp(fevfc,1);
  document.lung.mmv.value = nt2dp(mmv,1);
}

function vclear()
{
  document.lung.fvc.value = "";
  document.lung.fev.value = "";
  document.lung.fevfc.value = "";
  document.lung.mmv.value = "";
}


function nt2dp(num,dp)
{
<!-- rounds num to dp decimal places -->
  num=num*1+(0.55/Math.pow(10,dp));
  if (dp>0) dp=dp+1;
  b=Math.floor(num).toString().length+dp;
  return num.toString().substr(0,b);
}