@ -17,9 +17,13 @@
;; Copyright 2002 Joshua Sled <jsled@asynchronous.org>
;;
;; Simple function for testing:
( define ( gnc:foobar val ) val )
;; pretty literal copies of similar code from gnumeric-1.0.8, except we want
;; positive values to be returned [as gnucash will handle the credit/debit
;; appropriately]
;; positive values to be returned ( as gnucash will handle the credit/debit
;; appropriately )
( define ( gnc:ipmt rate per nper pv fv type )
( * -1 ( * rate
@ -41,8 +45,6 @@
( define ( gnc:pmt rate nper pv fv type )
( * -1 ( calc-pmt rate nper pv fv type ) ) )
( define ( gnc:foobar val ) val )
;;;;;
;; below: not-exposed/"private" functions, used by the "public" functions
;; above.
@ -72,3 +74,84 @@
rate ) ) )
)
;; This section added in 2005. Ludovic Nicolle
;; Formula to get the rate for a given period if there are yper in the year
;; And the official rate is compounded ycomp in the year.
;; For example, a mortgage being monthly has yper = 12
;; and if the posted rate is a plain annual rate, then ycomp = 1.
;; but if the posted rate is compounded semi-annually, as is the case in Canada,
;; then ycomp = 2.
;; this function can be used to enter the nominal rate in the formulas, without
;; pre-calculating the power function below.
( define ( gnc:periodic_rate rate yper ycomp )
( - ( expt ( + 1.0 ( / rate ycomp ) ) ( / ycomp yper ) ) 1.0 )
)
;; the three following functions with prefix gnc:cpd_ are more generic equivalents of
;; gnc:pmt, gnc:ipmt and gnc:ppmt above, with some differences.
;; First difference is that they take the annual nominal rate and two yearly frequencies:
;; rate is annual, not per period (the functions calculate it themselves)
;; yfreq determines the compounding frequency of the payed/charged interest
;; ycomp determines the compounding frequency of the annual nominal rate
;; Second difference is for rounding. My experience shows that all banks do not use
;; the exact same rounding parameters. Moreover, on top of that situation, numerical calculations
;; in gnucash using the original gnc:pmt, gnc:ipmt and gnc:ppmt functions above can also
;; create another set of rounding issues. Both problems create the "odd-penny imbalance" problem.
;; So the gnc:cpd_Zpmt functions do automatic rounding, the goal being to have PPMT = PMT - I
;; holding true for all calculated numbers. However, this won't fix the first problem if your bank
;; can't do proper maths and manual fixing of transactions will still be required.
;; One problem with the rounding procedure in these three functions is that it is always
;; rounding at the second decimal. This works great with dollars and euros and a lot of major
;; currencies but might well cause issues with other currencies not typically divided in 100.
;; I have not tested anything else than dollars.
;; If the automatic rounding causes issues for a particular case, one can always use the
;; equivalence of the cpd_ and non-cpd_ functions, by using periodic_rate() like this:
;; gnc:cpd_pmt( rate:yfreq:ycomp :nper:pv:fv:type)
;; is equivalent to gnc:pmt(periodic_rate(rate:yfreq:ycomp):nper:pv:fv:type)
;; On the opposite side, if you want the automatic rounding but don't understand how to use
;; the cpd_ functions, here is a quick example on how to convert original gnc:Zpmt
;; function calls. The typical setup is to use 'rate/yfreq' as the first parameter, so the
;; slution is to simply use yfreq for both yfreq and ycomp in the gnc:cpd_Zpmt calls, like this:
;; gnc:pmt( rate / yfreq :nper:pv:fv:type)
;; is equivalent to gnc:cpd_pmt( rate:yfreq:yfreq :nper:pv:fv:type)
( define ( gnc:cpd_ipmt rate yfreq ycomp per nper pv fv type )
( * 0.01
( round
( * -100 ( * ( gnc:periodic_rate rate yfreq ycomp )
( - 0 ( calc-principal pv
( calc-pmt ( gnc:periodic_rate rate yfreq ycomp ) nper pv fv type )
( gnc:periodic_rate rate yfreq ycomp ) ( - per 1 ) ) ) )
)
)
)
)
( define ( gnc:cpd_ppmt rate yfreq ycomp per nper pv fv type )
( let* (
( per_rate ( gnc:periodic_rate rate yfreq ycomp ) )
( pmt ( * -1 ( gnc:cpd_pmt rate yfreq ycomp nper pv fv type ) ) )
( ipmt ( * per_rate ( calc-principal pv pmt per_rate ( - per 1 ) ) ) )
)
(
* -1 ( + pmt ipmt )
)
)
)
( define ( gnc:cpd_pmt rate yfreq ycomp nper pv fv type )
( * 0.01
( round
( * -100
( calc-pmt ( gnc:periodic_rate rate yfreq ycomp ) nper pv fv type )
)
)
)
)
Joshua Sled
20 years ago