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Excel calculator
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module Excel | |
module Formulas | |
def pmt(rate, nper, pv, fv=0, type=0) | |
((-pv * pvif(rate, nper) - fv ) / ((1.0 + rate * type) * fvifa(rate, nper))) | |
end | |
def ipmt(rate, per, nper, pv, fv=0, type=0) | |
p = pmt(rate, nper, pv, fv, 0); | |
ip = -(pv * pow1p(rate, per - 1) * rate + p * pow1pm1(rate, per - 1)) | |
(type == 0) ? ip : ip / (1 + rate) | |
end | |
def ppmt(rate, per, nper, pv, fv=0, type=0) | |
p = pmt(rate, nper, pv, fv, type) | |
ip = ipmt(rate, per, nper, pv, fv, type) | |
p - ip | |
end | |
protected | |
def pow1pm1(x, y) | |
(x <= -1) ? ((1 + x) ** y) - 1 : Math.exp(y * Math.log(1.0 + x)) - 1 | |
end | |
def pow1p(x, y) | |
(x.abs > 0.5) ? ((1 + x) ** y) : Math.exp(y * Math.log(1.0 + x)) | |
end | |
def pvif(rate, nper) | |
pow1p(rate, nper) | |
end | |
def fvifa(rate, nper) | |
(rate == 0) ? nper : pow1pm1(rate, nper) / rate | |
end | |
end | |
end |
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