Class Calc

Calc provides methods to calculate part payment functions.

All rates are yearly rates, but they are calculated monthly. So a rate of 9 % is used 0.75% monthly. The first is the one we specify to the customers, and the second one is the one added each month to the account. The IRR uses the same notation.

The APR is however calculated by taking the monthly rate and raising it to the 12 power. This is according to the EU law, and will give very large numbers if the $pval is small compared to the $fee and the amount of months you repay is small as well.

All functions work in discrete mode, and the time interval is the mythical evenly divided month. There is no way to calculate APR in days without using integrals and other hairy math. So don't try. The amount of days between actual purchase and the first bill can of course vary between 28 and 61 days, but all calculations in this class assume this time is exactly and that is ok since this will only overestimate the APR and all examples in EU law uses whole months as well.