Entering formulas in scheduled transactions

[Derek Atkins]

Matthew Vanecek <mevanecek at yahoo.com> writes:

> no, no, you're right--if I pay extra principal, the interest changes. 
> I've just never done it, so didn't think about it that way.  However,
> the date my regular payment hits the bank doesn't affect the
> principal/interest split like with my auto loan.

Ahh...  Ok..

> Unfortunately, the druid formulas don't always reflect reality, and can
> even be way off sometimes.  For me, even a penny off is unacceptable--I
> require exactness in my financial picture.  If there were a way to
> specify a custom formula for anal retentives like myself, SX would
> probably be more attractive WRT entering loans.
> 
> My loan holders think that penny matters; guess I ought to, too...

I've noticed (well, other users have noticed and I've helped track
down) that some of this is due to truncation (generally of the
interest rate).  Some banks seem to truncate the rate(s) when
computing the payments.  You might want to play around and see what
happens if you truncate your periodic rate to, say, 4 significant
digits.  Does that better match what the bank says?

Perhaps we should let the user provide a "level of truncation" in
order to get the numbers to match properly?

-derek

-- 
       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
       warlord at MIT.EDU                        PGP key available