// Body Fat Calculator
// copyright 23rd April 2006, by Stephen Chapman
// permission to use this Javascript on your web page is granted
// provided that all of the code in this script (including these
// comments) is used without any alteration


function valButton(btn) 
{
	var cnt = -1;
	for (var i=btn.length-1; i > -1; i--) 
	{   
		if (btn[i].checked) {cnt = i; i = -1;}
	}
	if (cnt > -1) return btn[cnt].value;else return null;
}

function stripBlanks(fld) 
{
	var result = "";
	var c = 0;
	for (i=0; i < fld.length; i++) 
	{
		if (fld.charAt(i) != " " || c > 0) 
		{
			result += fld.charAt(i);if (fld.charAt(i) != " ") c = result.length;
		}	
	}
	return result.substr(0,c);
}

function maleFat(h,n,w) 
{
	return thou(495/(1.0324-0.19077*(Math.log(w-n)/Math.LN10)+0.15456*(Math.log(h)/Math.LN10))-450);
}

function femaleFat(h,n,w,r) 
{
	return thou(495/(1.29579-0.35004*(Math.log(w+r-n)/Math.LN10)+0.22100*(Math.log(h)/Math.LN10))-450);
}

function thou(n) 
{
	return Math.round(n*10)/10+'%';
}

function sex(thisform) 
{
	var s = valButton(thisform.s);thisform.r.disabled = (s != 'f');
}

function calc(thisform) 
{
	var s = valButton(thisform.s);
	
	if (s == null) 
	{
		alert("You must enter your gender");
		return false;
	}
	var d = valButton(thisform.d);
	if (d == null) 
	{
		alert("You must choose centimetres or inches");
		return false;
	}
	d = Number(d);
	var h = stripBlanks(thisform.h.value);
	if (h == '') 
	{
		alert("You must enter your height");
		thisform.h.focus();
		return false;
	}
	if (h != Number(h) || (h = Number(h*d)) < 100 || h > 250) 
	{
		alert("Invalid height entered");
		thisform.h.focus();
		return false;
	}
	var n = stripBlanks(thisform.n.value);
	if (n == '') 
	{
		alert("You must enter your neck size");
		thisform.n.focus();
		return false;
	}
	if (n != Number(n) || (n = Number(n*d)) < 20 || n > 60) 
	{
		alert("Invalid neck size entered");
		thisform.n.focus();return false;
	}
	var w = stripBlanks(thisform.w.value);
	if (w == '') 
	{
		alert("You must enter your waist size");
		thisform.w.focus();
		return false;
	}
	if (w != Number(w) || (w = Number(w*d)) < 30 || w > h) 
	{
		alert("Invalid waist size entered");
		thisform.w.focus();
		return false;
	}
	var r = 0;
	if (s == 'f') 
	{
		r = stripBlanks(thisform.r.value);
		if (r == '') 
		{
			alert("You must enter your hip size");
			thisform.r.focus();
			return false;
		}
		if (r != Number(r) || (r = Number(r*d)) < 40 || h > 200) 
		{
			alert("Invalid hip size entered");
			thisform.r.focus();
			return false;
		}
	}
	switch(s) 
	{
		case 'm': thisform.f.value = maleFat(h,n,w); 
		break; 
		case 'f': thisform.f.value = femaleFat(h,n,w,r);
	}
}