//Purpose: To find the monthly payments on a loan.
//Date: 9-9-05

	function calcpayment(amountvalue, yearsvalue, ratevalue) 
	{
		var loop          = 0;
		var balance       = amountvalue;
		var interest      = 0.0;
		var principal     = 0.0;
		var totalinterest = 0.0;
		
		var mpay      = document.getElementById("mpay"); 
		var charreturn = String.fromCharCode(13);                             											 //character return for line spacing
		var tab        = String.fromCharCode(27);                     											         //tab for formating
		
		var payment    = getPayment(amountvalue, yearsvalue, ratevalue);
		
		mpay.value = (Math.round(payment * 100) / 100);
	
		var yearsmessage     = "The total years must be larger than zero."
		var ratemessage      = "The rate must be larger than a negitive number."
		var principlemessage = "The principle must be larger than zero."
		
		datainteg(amountvalue, yearsvalue, ratevalue)                                                                    //funtion to check datainteg. 
		
		function datainteg(amountvalue, yearsvalue, ratevalue)
		{
			if (amountvalue <= 0)																						 
			{
		        alert(principlemessage)
        	}
        		else if(yearsvalue <= 0)
        		{
        			alert(yearsmessage)
        		}
        			else if(ratevalue < 0)
        			{
        				alert(ratemessage)
        			} 
        				else 
        				{
							for (loop = 1; loop <= (yearsvalue * 12); loop = loop + 1)                                   //changing from years to months for calcs.
							{
								interest      = balance * ratevalue / 1200;
								totalinterest = totalinterest + interest;
								principal     = payment-interest;
								balance       = balance - principal;
							}
						}
		}
	}

	function getPayment(amountvalue, yearsvalue, ratevalue) 
	{
		var acc    = 0;
		var looper = 0;
		var base   = 1 + ratevalue / 1200;
		
		for (looper = 1; looper <= (yearsvalue * 12); looper = looper + 1) 
		{
		    acc = acc + Math.pow(base, -looper); 
		}
		
		return amountvalue/acc;
	}