canadian mortgages in the SX editor
Ludovic Nicolle
lnicolle at chezludo.com
Sun Feb 27 18:06:41 EST 2005
Hey guys,
so this is my first post, so be indulgent if possible. thanks.
As a canadian user trying to use the Loan Druid and SX editor, one
feature that was missing was the ability to specify a nominal interest
rate that has an implicit compounding frequency that is different than
the actual compounding frequency of the interest paid.
(Yes I know, this sounds weird, but this is the way canadian mortgage
rates work, probably because 200 years ago doing a multiplication was
more costly than actually building the house, so they reduced the
number of calculations done.)
Anyway, there is a somewhat easy way to translate the canadian posted
rate to an effective periodic rate. One can use that rate with the
"standard" formula and get the good results, but you have to know the
proper formula, and enter it properly in the Sx editor, and know scheme
keywords. Not very user friendly.
So I have created a patch that contains 4 functions. One to do that
translation of nominal to effective rates based on the 2 compounding
frequencies. Three other functions are the cpd equivalent of the
gnc:pmt, gnc:ipmt and gnc:ppmt functions, with the conversion builtin,
so it's easier to use in the SX editor.
One more feature that was bugging me while working on this is that the
sum of interest and principal was often not equal to the payment. So
the the 3 cpd_ functions in the patch have a builtin rounding at the
2nd decimal. This precision is hardcoded, so i don't really like it,
but I think it can be fixed in a later patch.
So i created this bug http://bugzilla.gnome.org/show_bug.cgi?id=168700
with the patch attached.
jsled, this is your realm, so I guess you are the one who should give
me the most feedback. ;-)
Ludo
More information about the gnucash-devel
mailing list