Finance Functions:
The Interest Rate

The InterestRate() function is used to find the interest applied to a loan. Its syntax is:

Extended __fastcall InterestRate(int NPeriods,
                                 constExtended Payment,
                                 const Extended PresentValue,
                                 const Extended FutureValue,
                                 TPaymentTime PaymentTime);

All of the arguments are the same as described for the InterestPayment() function. Here is an example:

//---------------------------------------------------------------------------
void __fastcall TForm1::btnCalculateClick(TObject *Sender)
{
	Extended Present, Future, Payments, Rate;
	int NPeriod;
	Present = StrToFloat(edtPresent->Text);
	Future = StrToFloat(edtFuture->Text);
	Payments = StrToFloat(edtPayments->Text);
	NPeriod = StrToInt(edtNPeriods->Text);
	
	Rate = InterestRate(NPeriod, Payments, Present, Future, ptEndOfPeriod) * 12 * 100;
	AnsiString Value = FloatToStrF(Rate, ffGeneral, 3, 2);
	edtRate->Text = Value + "%";
}
//---------------------------------------------------------------------------