question about formulas in mortgage/loan druid

[Derek Atkins]

Unfortunately there's no way to compute the correct amount of interest based on
the current balance.  The Principal and Interest computations are all based on
the initial bank values.  This means that if you pre-pay principal then it wont
take that into account in future P vs. I computations.  You would need a
"getcurrentbalance()" function to plug into the ppmt() and ipmt() functions in
order to compute the principal and interest amounts based on the current
balance of an account.

-derek

Quoting Alan Munter <munter at gmail.com>:

> I was trying to set up a loan in the druid and I am a bit confused
> about what all of the arguments to the ipmt, ppmt, and pmt functions
> are.
> 
> I went through the druid and set up a loan for 10000, 24 months, 3.9%
> interest, and at the end Review screen I can see what the amortization
> would be which looks correct.  The payment, pmt, is approximately $400
> total per month.
> 
> However, those are the bank terms of the loan.  I would like to repay
> the loan faster, so I would like the pmt amount to be, for example,
> $450 per month instead of $400.  Can I just go back and edit the
> scheduled transaction and in the "Credit Formula" replace
> pmt(0.039/12:24:10000:0:0) with the number 450 and leave the two Debit
> formulas alone to let them calculate it correctly?
> 
> Thanks a lot and thanks to the developers for not just making a great
> program but also in the process teaching me about double-entry
> bookkeeping.
> 
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-- 
       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