Evaluates the payment on the principal for a specified period.

rate—Interest rate.

period—Payment period.

n_periods—Total number of periods.

present_value—The current value of a stream of future payments, after discounting the payments using some interest rate.

future_value—The value, at some time in the future, of a current amount and a stream of payments.

when—Time in each period when the payment is made, either 0 for at the end of period or 1 for at the beginning of period.

result—The payment on the principal for a given period. If no result can be computed, NaN is returned.

Double—If present and nonzero, double precision is used.

Function PRINC_PAYMENT computes the payment on the principal for a given period. It is computed using the following:

where paymenti is computed from the function PAYMENT for the ith period and interesti is calculated from the function INT_PAYMENT for the ith period.

In this example, PRINC_PAYMENT computes the principal paid for the first year on a 30-year $100,000 loan with an annual interest rate of 8%. The payment is made at the end of each year.

PRINT, PRINC_PAYMENT(0.08, 1, 30, 100000., 0., 0)

; PV-WAVE prints: -882.742