Thread: Excel RATE() function in Java behaving a bit differently

Hi guys,

Just wanted to check something. I have the following function below which is the equivalent of the RATE function in Excel

In Excel, if I do the following in any cell: =RATE(68, -118161.59, 4146470.27) - it gives me: 2.2014989%

However, the below code gives me: 0.0220150136..

I am expecting it to give me 0.0022014989

It is only marginally out, but can anyone point me why it is marginally out?

Any help would be much appreciated

	public static void main(String[] args) 
	{
		double rate1 = Financials.rate(68, 118161.59, 4146470.27);
		System.out.println(rate1);
		System.out.println("finished");
 
	}

	public static double rate(double nper, double pmt, double pv)
	{       
	    double error = 0.0000001; 
	    double high =  1.00; 
	    double low = 0.00;
 
	    double rate = (2.0 * (nper * pmt - pv)) / (pv * nper);
 
	    while(true) {
	        // check for error margin
	        double calc = Math.pow(1 + rate, nper);
	        calc = (rate * calc) / (calc - 1.0);
	        calc -= pmt / pv;
 
	        if (calc > error) {
	            // guess too high, lower the guess
	            high = rate;
	            rate = (high + low) / 2;
	        } else if (calc < -error) {
	            // guess too low, higher the guess
	            low = rate;
	            rate = (high + low) / 2;
	        } else {
	            // acceptable guess
	            break;
	        }
	    }
 
	    //System.out.println("Rate : "+rate);       
	    return rate; 
	}

Can you post the code showing the new rate() method that was rewritten to use the BigDecimal class?

--- Update ---

Also posted at: Excel RATE() function in Java behaving slightly differently