Robert Helewka
a2420ed692
Reorganize Palladium codebase into a modular architecture with `core/` shared logic and `app/` Streamlit UI, separating per-study assets into `studies/YYYYMM_<Vendor>/` folders containing notebooks, seed data, and configuration. Update README to reflect new structure, add `.gitignore` entries for `.env` and study exports, and refresh component documentation.
64 lines
1.9 KiB
Python
64 lines
1.9 KiB
Python
"""
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Payback period.
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Linear interpolation within the crossing year: returns the moment when the
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running net cashflow first turns non-negative.
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Inputs are *risk-adjusted, undiscounted* cashflows by convention (TEI shows
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"<6 months" payback for the Amazon Connect composite using the risk-adjusted
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nominal cashflows from the Cash Flow Analysis table).
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"""
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from __future__ import annotations
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from collections.abc import Iterable
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def payback_years(
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initial_cost: float,
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yearly_net_benefits: Iterable[float],
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) -> float | None:
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"""
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Years until cumulative net benefits cover the initial cost.
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Args:
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initial_cost: positive number — undiscounted year-0 outlay.
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yearly_net_benefits: sequence of (benefits − costs) per year, Y1+.
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Returns:
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Float number of years, or ``None`` if payback is never reached
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within the supplied horizon.
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Example::
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>>> # Amazon Connect: initial cost $1.196M, Y1 net $19.998M
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>>> # → ~0.06 years ≈ 0.7 months — well under 6 months.
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>>> round(payback_years(1_196_250, [19_997_953, 31_562_489, 47_443_905]), 3)
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0.06
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"""
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remaining = float(initial_cost)
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if remaining <= 0:
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return 0.0
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cumulative_year = 0
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for cf in yearly_net_benefits:
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cumulative_year += 1
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cf = float(cf)
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if cf <= 0:
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remaining += -cf # net loss this year increases the gap
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continue
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if cf >= remaining:
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# Crossing happens partway through this year.
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fraction = remaining / cf
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return (cumulative_year - 1) + fraction
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remaining -= cf
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return None
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def payback_months(
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initial_cost: float,
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yearly_net_benefits: Iterable[float],
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) -> float | None:
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"""Same as :func:`payback_years`, expressed in months."""
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yrs = payback_years(initial_cost, yearly_net_benefits)
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return yrs * 12.0 if yrs is not None else None
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