41C/CV root finders

[Ángel Martin]

(05-28-2015 09:59 AM)Dieter Wrote:  Here's another, very simple method:

Code:

i0 = 2 / n * (PV + n*PMT + FV) / (FV – PV)

The estimate is the same for BEGIN and END mode. Here the denominator only becomes zero if FV = PV, which does not make much sense anyway. ;-)

I'll try this one first - easier to fit in the current room available. Will report results when done.

I agree if FV = PV the user deserves to get an error message, ha!

As to why the accuracy isn't 13-digits in the result - I was trying to avoid instabilities in the Newton algorithm, which happen due to oscillations around the result. I probably went overboard since the code checks that the delta be less than 1 E-8 and not 1 E-10 - I just assumed that many decimal digits don't make much sense for the nature of the variable, the interest rate (where anything beyond 2 decimal digits will probably be frowned at).

ÁM