/// <summary>
/// Returns the interest payment for a given period for an investment, based on periodic constant payments and a
/// constant interest rate.
/// </summary>
/// <param name="rate">Annual Interest Rate.</param>
/// <param name="period">Period.</param>
/// <param name="numberPeriods">Number of periods.</param>
/// <param name="presentValue">Present value.</param>
/// <param name="futureValue">Future value.</param>
/// <param name="due">Specifies when values are Due, at the beginning or at the end of the period.</param>
/// <returns></returns>
public double InterestPayment(double rate, short period, short numberPeriods, double presentValue, double futureValue, DueDate due)
{
short auxiliaryPeriod;
auxiliaryPeriod = due != DueDate.EndOfPeriod ? (short)2 : (short)1;
if (period <= 0 || period >= numberPeriods + 1)
{
throw new ArgumentException("Invalid Argument Value", "period");
}
if (due != DueDate.EndOfPeriod && period == 1)
{
return(0);
}
var payment = new Pmt().PaymentInternal(rate, numberPeriods, presentValue, futureValue, due);
if (due != DueDate.EndOfPeriod)
{
presentValue += payment;
}
var internalFutureValue = new IntFv().FutureValueInternal(rate, (short)(period - auxiliaryPeriod), payment,
presentValue, DueDate.EndOfPeriod);
return(internalFutureValue * rate);
}
/// <summary>
/// Returns the capital payment for a given period for an investment based on periodic,
/// constant payments and a constant interest rate.
/// </summary>
/// <param name="rate">Annual Interest Rate.</param>
/// <param name="period">Period.</param>
/// <param name="numberPeriods">Number of periods.</param>
/// <param name="presentValue">Present (principal) value.</param>
/// <param name="futureValue">Future value.</param>
/// <param name="due">Specifies when values are Due, at the beginning or at the end of the period.</param>
/// <returns></returns>
public double CapitalPayment(double rate, short period, short numberPeriods, double presentValue, double futureValue, DueDate due)
{
if (period <= 0 || period >= numberPeriods + 1)
{
throw new ArgumentException("Invalid Argument Value", "period");
}
var payment = new Pmt().PaymentInternal(rate, numberPeriods, presentValue, futureValue, due);
var interest = new IPmt().InterestPayment(rate, period, numberPeriods, presentValue, futureValue, due);
return(payment - interest);
}
