Chapter 9: Special Functions

principal_payment

Evaluates the payment on the principal for a specified period.

Synopsis

#include <imsl.h>

float imsl_f_principal_payment (float rate, int period, int n_periods, float present_value, float future_value, int when)

The type double function is imsl_d_principal_payment.

Required Arguments

float rate   (Input)
Interest rate.

int period   (Input)
Payment period.

int n_periods   (Input)
Total number of periods.

float present_value   (Input)
The current value of a stream of future payments, after discounting the payments using some interest rate.

float future_value   (Input)
The value, at some time in the future, of a current amount and a stream of payments.

int when   (Input)
Time in each period when the payment is made, either IMSL_AT_END_OF_PERIOD or IMSL_AT_BEGINNING_OF_PERIOD. For a more detailed discussion on when see the Usage Notes section of this chapter.

Return Value

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

Description

Function imsl_f_principal_payment computes the payment on the principal for a given period.

It is computed using the following:

where paymenti is computed from imsl_f_payment for the ith period,
interesti is calculated from imsl_f_interest_payment for the ith period.

Example

In this example, imsl_f_principal_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.

 

#include <stdio.h>

#include "imsl.h"

 

void main()

{

  float rate = .08;

  int period = 1;

  int n_periods = 30;

  float present_value = 100000.00;

  float future_value = 0.0;

  int when = IMSL_AT_END_OF_PERIOD;

  float principal;

 

  principal = imsl_f_principal_payment (rate, period, n_periods,

                                   present_value, future_value, when);

  printf ("The payment on the principal for the first year of \n");

  printf ("the $100,000 loan is $%.2f.\n", principal);

}

Output

The payment on the principal for the first year of

the $100,000 loan is $-882.74.


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