问题
I want to use Excel PMT function in Javascript. The parameter would be
Pmt( interest_rate, number_payments, PV, FV, Type )
interest_rate : the interest rate for the loan.
number_payments : the number of payments for the loan.
PV : the present value or principal of the loan.
FV : It is the future value or the loan amount outstanding after all payments have been made.
Type is : It indicates when the payments are due. Type can be one of the following values:
0, 1
You can refer : http://www.techonthenet.com/excel/formulas/pmt.php
this is the code I use, I am stuck in last parameter. Which is "type is" 0 or 1. How it effect the calculations please.
function PMT (ir, np, pv, fv ) {
/*
ir - interest rate per month
np - number of periods (months)
pv - present value
fv - future value (residual value)
*/
pmt = ( ir * ( pv * Math.pow ( (ir+1), np ) + fv ) ) / ( ( ir + 1 ) * ( Math.pow ( (ir+1), np) -1 ) );
return pmt;
}
I need it in plain Javascript and not in jQuery please.
回答1:
The easiest way to understand the impact of the Type parameter is to try the following values: Annual Interest = 12%, # of Months = 1, Present Value = 100
When Type=0 (the default), the PMT() function will yield 101
When Type=1, the PMT() function will yield 100
With Type=0, the interest is computed for 1 month because the payment is assumed to be at the end of the month. For Type=1, the interest is computed for 0 months because the payment is at the beginning of the month.
回答2:
this is my version of PMT function after some googling:
function PMT(ir, np, pv, fv, type) {
/*
* ir - interest rate per month
* np - number of periods (months)
* pv - present value
* fv - future value
* type - when the payments are due:
* 0: end of the period, e.g. end of month (default)
* 1: beginning of period
*/
var pmt, pvif;
fv || (fv = 0);
type || (type = 0);
if (ir === 0)
return -(pv + fv)/np;
pvif = Math.pow(1 + ir, np);
pmt = - ir * pv * (pvif + fv) / (pvif - 1);
if (type === 1)
pmt /= (1 + ir);
return pmt;
}
Example What is the monthly payment needed to pay off a $200,000 loan in 15 years at an annual interest rate of 7.5%?
ir = 0.075 / 12
np = 15 * 12
pv = 200000
pmt = PMT(ir, np, pv).toFixed(2) = -1854.02
payoff = pmt * np = -333723.6
回答3:
here in my PMT version
PMT: function(rate, nperiod, pv, fv, type) {
if (!fv) fv = 0;
if (!type) type = 0;
if (rate == 0) return -(pv + fv)/nperiod;
var pvif = Math.pow(1 + rate, nperiod);
var pmt = rate / (pvif - 1) * -(pv * pvif + fv);
if (type == 1) {
pmt /= (1 + rate);
};
return pmt;
},
//// Call the PMT
var result = PMT(6.5/1200 , 30*12 , 65000 , 0 , 0);
console.log(result);
//// result : -410.8442152704279
/// Other as well IPMT and PPMT
IPMT: function(pv, pmt, rate, per) {
var tmp = Math.pow(1 + rate, per);
return 0 - (pv * tmp * rate + pmt * (tmp - 1));
},
PPMT: function(rate, per, nper, pv, fv, type) {
if (per < 1 || (per >= nper + 1)) return null;
var pmt = this.PMT(rate, nper, pv, fv, type);
var ipmt = this.IPMT(pv, pmt, rate, per - 1);
return pmt - ipmt;
},
回答4:
I solved it using the following function, thanks to the site tvmcalcs.com, An Example with Advance Payments.
function pmt(monthlyRate, monthlyPayments, presentValue, residualValue, advancedPayments) {
t1 = 1+monthlyRate
t2 = Math.pow(t1,monthlyPayments)
t3 = Math.pow(t1,(monthlyPayments-advancedPayments))
return (presentValue-(residualValue/t2))/(((1-(1/(t3)))/monthlyRate)+advancedPayments);
}
or if you have, as in our case, a annualRate
function pmtWithAnnualRate(annualRate, monthlyPayments, presentValue, residualValue, advancedPayments) {
monthlyRate = annualRate / 1200
t1 = 1 + monthlyRate
t2 = Math.pow(t1,monthlyPayments)
t3 = Math.pow(t1,(monthlyPayments-advancedPayments))
return (presentValue-(residualValue/t2))/(((1-(1/(t3)))/monthlyRate)+advancedPayments);
}
来源:https://stackoverflow.com/questions/5294074/pmt-function-in-javascript