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DOC: clarify pmt cash-flow signs #157

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DOC: clarify pmt cash-flow signs #157

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a52eb56
DOC: clarify pmt cash-flow signs
naseweisssss Sep 26, 2026
ad8b847
DOC: simplify remaining loan balance example
naseweisssss Sep 26, 2026
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12 changes: 10 additions & 2 deletions numpy_financial/_financial.py
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Original file line number Diff line number Diff line change
Expand Up @@ -317,9 +317,10 @@ def pmt(rate, nper, pv, fv: Any = 0, when: _When = 'end'):
nper : array_like
Number of compounding periods
pv : array_like
Present value
Present value. For a loan, the amount received is positive.
fv : array_like, optional
Future value (default = 0)
Future cash balance (default = 0). For a loan with positive `pv`,
use a negative value for a balance that remains to be repaid.
when : {{'begin', 1}, {'end', 0}}, {string, int}
When payments are due ('begin' (1) or 'end' (0))

Expand Down Expand Up @@ -377,6 +378,13 @@ def pmt(rate, nper, pv, fv: Any = 0, when: _When = 'end'):
today, a monthly payment of $1,854.02 would be required. Note that this
example illustrates usage of `fv` having a default value of 0.

For a $100 loan with no interest, ten payments of $8 leave $20 owed.
Use ``fv=-20`` for this remaining debt; payments are negative because
they represent money paid out:

>>> float(npf.pmt(0, 10, 100, fv=-20))
-8.0

"""
when = _convert_when(when)
(rate, nper, pv, fv, when) = map(np.array, [rate, nper, pv, fv, when])
Expand Down