//Build an array to keep the last calculated value.

anchor = new Array(0,0,0,0,0);

function calculate(savingsform)
{
  //Validate incoming fields 
  
  
    pv = savingsform.PRESENT_VALUE.value;
    fv = savingsform.SAVINGS_GOAL.value;
    np = savingsform.SAVINGS_PERIOD.value;
    pmt = savingsform.DEPOSIT_AMT.value;
    ir = savingsform.INTEREST_RATE.value;
    paymentperiod = 12;
    durationperiod = savingsform.SAVINGS_PERIOD_FREQ.options[savingsform.SAVINGS_PERIOD_FREQ.selectedIndex].value;


	if ((pv.length > 0) && (pv < 0))
	{
	   alert('Initial Investment must be a positive number');
	   return;
	}
	
	if ((pmt.length > 0) && (pmt < 0))
	{
	   alert('Monthly Deposit must be a positive number');
	   return;
	}
	

	if ((np.length > 0) && (np < 0))
	{
	   alert('Saving Period must be a positive number');
	   return;
	}
	
	if ((ir.length > 0) && (ir < 0))
	{
	   alert('Interest Rate must be a positive number');
	   return;
	}
	
	if ((fv.length > 0) && (fv < 0))
	{
	   alert('Savings Goal must be a positive number');
	   return;
	}


	if ((pv.length > 0) && (isNumeric(pv) == false))
	{
	   alert('Initial Investment must be numeric');
	   return;
	}
	
	if ((pmt.length > 0) && (isNumeric(pmt) == false))
	{
	   alert('Monthly Deposit must be numeric');
	   return;
	}
	

	if ((np.length > 0) && (isNumeric(np) == false))
	{
	   alert('Saving Period must be numeric');
	   return;
	}
	
	if ((ir.length > 0) && (isNumeric(ir) == false))
	{
	   alert('Interest Rate must be numeric');
	   return;
	}
	
	if ((fv.length > 0) && (isNumeric(fv) == false))
	{
	   alert('Savings Goal must be a numeric');
	   return;
	}

    //Store incoming values in an array
	
    tmpInValues = new Array(pv, pmt, ir, np, fv);
	
    m = 0;
    blankCount=0;
    var blankIndex;
    for(m=0;m<tmpInValues.length;m++) 
    {
        if(tmpInValues[m] == '') 
		{
	     	blankCount++;
			blankIndex = m;
		}
    }

	//Determine how many of the fields are blank
	
    if(blankCount > 1)
    {
	alert('Please fill in all but one entry');
    } 
    else 
    {
	if(!(blankIndex >= 0)) 
	{
        //find the last value calculated from anchor
	    var y;
	    for(y=0;y<anchor.length;y++) 
	    {
		if(anchor[y] == 1) 
		{
			blankIndex = y;
		}
	    }
	}
	
	for(w=0;w<anchor.length;w++) 
	{
	    anchor[w] = 0;
	    if(w==blankIndex) 
	    {
		anchor[w] = 1;
	    }		
	}

	if (np != "") 
	{
	   np = np * paymentperiod * durationperiod;
	} 
	else
	{
	    np = 0;
	} 
	
	if(ir != "") 
	{
	    ir = (ir / paymentperiod ) / 100 ;
	}
	
	ir = parseFloat(ir);
	np = parseFloat(np);
	fv = parseFloat(fv);
	pmt = parseFloat(pmt);
	pv = parseFloat(pv);
		
   	switch(blankIndex.toString()) 
	{
        case "0":
 		savingsform.PRESENT_VALUE.value = PresentValue();
		break;
        case "1":
		savingsform.DEPOSIT_AMT.value = DepositAmount();
		break;
        case "2":
		savingsform.INTEREST_RATE.value = InterestRate();
		break;
        case "3":
		savingsform.SAVINGS_PERIOD.value = SavingsPeriod();
		break;
        case "4":
		savingsform.SAVINGS_GOAL.value = FutureValue();
		break;
	}	
  }	
}		

function PresentValue() 
{
	    pmt = pmt * -1;

		if(ir == 0) 
		{
			pv = -(fv + (pmt * np));
		}
		else {
			q1 = Math.pow(1 + ir,-np);
			q2 = Math.pow(1 + ir,np);
			pv = (q1 * (fv * ir - pmt + q2 * pmt))/ir;
		}
        return RoundToHundreths(pv);
}  // End of Present Value

function FutureValue()
{
	if(ir == 0) 
	{
	  fv = -(pv + (-pmt * np));
	}
	else 
	{
		q = Math.pow(1+ir,np);
		fv = (-pmt + q * pmt + ir * q * pv)/ir;
	}
	return RoundToHundreths(fv);
}  // End of FutureValue


function SavingsPeriod()
{
	pmt = pmt * -1;
	pv = pv * -1;
	
	if(ir == 0)
	{
		if(pmt != 0) 
		{
			np = - (fv + pv)/pmt;
		}
		else 
		{
			alert("Divide by zero error.");
		}
	}
	else 
	{
		np = Math.log((-fv * ir + pmt)/(pmt + ir * pv))/ Math.log(1 + ir);
	}
	if(np == 0) 
	{
		alert("Can't compute Number of Periods for the present values.");
	}
	else 
	{
	    var durationmult = 0;
        if (durationperiod == 1){durationmult = .08333333333;}
        if (durationperiod == .25){durationmult = .3333333333;}
        if (durationperiod == .083333333333){durationmult = 1;}
        if (durationperiod == .019165364791){durationmult = 4.3480;}								
		return RoundToHundreths(np * durationmult);
	}
} //End of Savings Period


function DepositAmount()
{	
	pv = pv * -1;
	
	if(ir == 0.0) 
	{
		if(np != 0) 
		{
			pmt =  (fv + pv)/np;
		}
		else 
		{
			alert("Divide by zero error.");
		}
	}
	else 
	{
		q = Math.pow(1 + ir,np);
		pmt = ((ir * (fv + q * pv))/(-1 + q));		
	}

	return RoundToHundreths(pmt);
	
}//End of Deposit Amount
	
	
function DepositAmountIntCalc(pv, ir)
{

	ir = parseFloat(ir/paymentperiod/100);

		
	if(ir == 0.0) 
	{
		if(np != 0) 
		{
			pmt = - (fv + pv)/np;
		}
		else 
		{
			alert("Divide by zero error.");
		}
	}
	else 
	{
		q = Math.pow(1 + ir,np);
		pmt = ((ir * (fv + q * pv))/(-1 + q));		
	}

	return RoundToHundreths(pmt);
	
}//End of Deposit Amount for Interest  Calc	
	
function InterestRate()
{	
    initialInterest = 10000;
    var paymentTmp = 0;
 	var low = 0;
	var high = 10000;	
	var realPayment = parseFloat(pmt);	

	low = parseFloat(low);
	high = parseFloat(high);
	paymentperiod = parseFloat(paymentperiod);

	pv = pv * -1;
	
	if ((fv - (-pv + (np * realPayment))) < 0) 
	{
   	 	alert('This calculation resulted in negative interest.  Please increase the Savings Goal, or reduce the Savings Period, Initial Investment or Monthly Deposit.');
        return 'Error';
	}
	else
	{

		for( i = 0; i < 200; i++) 
	    {
		 	paymentTmp = DepositAmountIntCalc(pv, initialInterest);	
		
			   if ( paymentTmp < realPayment) {
				   high = initialInterest
		       } else if(paymentTmp > realPayment) {
	   	  	   low = initialInterest;
		          } else {
		   		  break;
		   		}
    
       	   initialInterest = low + ((high - low) /2);
	    }   
	}

	return RoundToHundreths(initialInterest);

} //End of  InterestRate	
	

function isNumeric(strString)
   //  check for valid numeric strings	
{
   var strValidChars = "0123456789.-";
   var strChar;
   var blnResult = true;

   //  test strString consists of valid characters listed above
   for (i = 0; i < strString.length && blnResult == true; i++)
      {
      strChar = strString.charAt(i);
      if (strValidChars.indexOf(strChar) == -1)
         {
         blnResult = false;
         }
      }
   return blnResult;
}

function RoundToHundreths(iValue) {

	// Round the value to Hundreths
	iValue = Math.round(iValue*100);
	iValue = iValue / 100;

	//Give me two decimal places
	
	iValue = iValue.toString();
	
	var posDecimalPoint=  iValue.indexOf('.');
	if (posDecimalPoint == -1) {
		iValue += ".00";
	} else if ( length - posDecimalPoint == 2) {
		iValue += "0";
	} else if (length - posDecimalPoint == 1) {
		iValue += "00";
	} 
	
	return iValue;
	
}
//-->
//-->

<!--
function replace_punct(element) { //v2.0
   var c= element.value; 
   c=c.replace(/[|,|\$]| /g, '');
   element.value = c;
   return true;
}