Calculator Modules

This page outlines the Python implementations of the IHACPA NWAU calculators. Each module loosely mirrors a SAS program from the official calculator package. The repository documents the 2026-27 NEP26 calculator set as available and listed, but this page does not claim parity validation against extracted IHACPA outputs unless tests explicitly establish it. The shared classification preflight validator is available in nwau_py.classification_validation, but this page does not claim it is wired into every calculator or CLI entry point yet.

Supported pricing years

Year	NWAU price	Acute classification	Non-admitted classification	Notes
NEP26 (2026-27)	$7,418/NWAU(26)	AR-DRG v12.0	Tier 2 v10.0	Transition from AR-DRG v11.0 (acute) and Tier 2 v7 (non-admitted). AECC v1.1, AMHCC v1, AN-SNAP v5, UDG v1.3 unchanged. Not yet validated; parity is only claimed when tests prove it.

Module	SAS source	Notes
acute	NWAU25_CALCULATOR_ACUTE.sas	Calculates NWAU25 for acute admitted episodes. Implements ICU hour logic, length of stay categories and private patient adjustments using pandas operations. 2026-27 documentation coverage notes AR-DRG v12.0 for admitted acute and Tier 2 v10.0 for non-admitted. An opt-in Rust-backed acute 2025 adapter is also available via calculate_acute_rust_2025().
ed	NWAU25_CALCULATOR_ED.sas	Handles Emergency Department/Service activity. Supports UDG and AECC classifications with remoteness and indigenous adjustments.
mh	NWAU25_CALCULATOR_MH.sas	Implements the mental health consumer model. Applies private patient services and accommodation adjustments.
subacute	NWAU25_CALCULATOR_SUBACUTE.sas	Calculates NWAU25 for subacute admitted activity based on SNAP.
outpatients	NWAU25_CALCULATOR_OUTPATIENTS.sas	For non‑admitted clinic activity. Applies remoteness and indigenous adjustments.
adjust	Calculate Adjusted NWAU.sas	Combines base NWAU with Hospital Acquired Complication (HAC) and Avoidable Hospital Readmission (AHR) adjustments.

The SAS programs are stored under archive/sas/NEP25_SAS_NWAU_calculator/calculators. The Python functions focus on the core weighting formulae and use pandas for data manipulation. See the source code of each module for details of the translation.

Community mental health still needs an official-source fixture pack before the mh surface can be validated against extracted IHACPA outputs. The current gap record and pricing-year caveats are documented in conductor/tracks/community_mental_health_calculator_20260512/fixture_gaps.md.

For the 2026-27 NEP26 release, the calculators are listed as available documentation references, but validation parity is intentionally not claimed in this page unless tests establish it.

For the current feature-to-tool incorporation summary, see the IHACPA Tool Coverage Matrix at conductor/ihacpa-tool-coverage-matrix.md.

For cross-language parity work, the package also ships manifest-driven fixture packs under tests/fixtures/golden/, with the acute pilot pack at tests/fixtures/golden/acute_2025/. The shared loader helpers live in nwau_py.fixtures and let Python tests consume the same manifest and payload layout used by future runners.

Usage examples

Below are minimal examples for each calculator. Dataframes should provide the columns referenced in the IHACPA documentation.

Acute

from nwau_py.calculators import AcuteParams, calculate_acute
result = calculate_acute(acute_df, AcuteParams())

Emergency department

from nwau_py.calculators import EDParams, calculate_ed
result = calculate_ed(ed_df, EDParams())

Mental health

from nwau_py.calculators import MHParams, calculate_mh
result = calculate_mh(mh_df, MHParams())

Subacute

from nwau_py.calculators import SubacuteParams, calculate_subacute
result = calculate_subacute(sa_df, SubacuteParams())

Outpatients

from nwau_py.calculators import OutpatientParams, calculate_outpatients
result = calculate_outpatients(op_df, OutpatientParams())

Adjustment

from nwau_py.calculators import calculate_adjusted_nwau
result = calculate_adjusted_nwau(weight_df)

Command line interface

The calculators can also be executed from the command line using python -m nwau_py.cli.main. Each calculator is available as a subcommand:

python -m nwau_py.cli.main acute input.csv --output out.csv --year 2025

Use ed or non-admitted for emergency and outpatient activity. Options such as --params select the weights directory while --icu/--no-icu and --covid/--no-covid toggle specific adjustments.

Debugging and cleanup

Each parameter dataclass includes two optional flags:

• debug_mode – when True intermediate columns (those beginning with underscores) are retained in the returned dataframe. The default False mimics the SAS calculators by dropping these helper fields.
• clear_data – when True any cached reference tables under .cache are removed after calculation completes.

Example usage:

params = AcuteParams(debug_mode=True)
df = calculate_acute(data, params)