Module: LoanCreator::ExcelFormulas

Included in:
Standard
Defined in:
lib/loan_creator/excel_formulas.rb

Overview

Source: gist.github.com/mattetti/1015948

Instance Method Summary collapse

Instance Method Details

#ipmt(rate, per, nper, pv, fv = 0, type = 0) ⇒ Object

Returns the interest payment for a given period for an investment based on periodic, constant payments and a constant interest rate.



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# File 'lib/loan_creator/excel_formulas.rb', line 6

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

#ppmt(rate, per, nper, pv, fv = 0, type = 0) ⇒ Object

Returns the payment on the principal for a given period for an investment based on periodic, constant payments and a constant interest rate.



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# File 'lib/loan_creator/excel_formulas.rb', line 14

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