Introduce the interest rate chart to summary section about isumm HOT 3 CLOSED

Should we subtract C_i as well, to prevent deposits and withdrawals in the current month from impacting the interest rate? Unit tests will definitely help here :)

from isumm.

I would say no, but maybe it seems that we should improve documentation.

From Readme.md:

Withdrawal and Deposit: used to calculate month-by-month profit.
Balance: for the sake of simplification, only one is considered per month. If you added more than one balance operations, only the most-recent is used.

What I meant is that balance is already the end-of-the-month balance. This means that all deposits and withdrawals are already accounted as well as daily interested and all that (i.e. when the first deposit occurs in the middle of the month). The rationale is to leave the to the bank the hard work.

What do you think?

from isumm.

Actually, you're correct.

The formula seems to be

Ii,i-1 = (B_i - (B_i-1 + C_i)) / ((B_i-1 + C_i)))

And yeah, unit tests FTW

from isumm.