[DRAFT] Allow arbitrary IAM function in pvlib.iam.marion_diffuse

.github/workflows/flake8.yml

@@ -12,7 +12,7 @@ jobs:
         with:
           python-version: '3.11'
       - name: Install Flake8 5.0.4 linter
-        run: pip install flake8==5.0.4  # use this version for --diff option
+        run: pip install flake8==5.0.4  # use this version for --diff option, should match version in pyproject.toml
       - name: Setup Flake8 output matcher for PR annotations
         run: echo '::add-matcher::.github/workflows/flake8-linter-matcher.json'
       - name: Fetch pull request target branch

docs/examples/spectrum/spectral_factor.py

@@ -46,7 +46,8 @@
 # spectral factor functions:
 #
 # - :py:func:`~pvlib.spectrum.spectral_factor_sapm`, which requires only
-#   the absolute airmass, :math:`AM_a`
+#   the absolute airmass, :math:`AM_a` and five SAPM coefficients :math:`A0` -
+#   :math:`A4`
 # - :py:func:`~pvlib.spectrum.spectral_factor_pvspec`, which requires
 #   :math:`AM_a` and the clearsky index, :math:`k_c`
 # - :py:func:`~pvlib.spectrum.spectral_factor_firstsolar`, which requires
@@ -104,7 +105,14 @@
 module = pvlib.pvsystem.retrieve_sam('SandiaMod')['LG_LG290N1C_G3__2013_']
 #
 # Calculate M using the three models for an mc-Si PV module.
-m_sapm = pvlib.spectrum.spectral_factor_sapm(airmass_absolute, module)
+m_sapm = pvlib.spectrum.spectral_factor_sapm(
+    airmass_absolute,
+    module["A0"],
+    module["A1"],
+    module["A2"],
+    module["A3"],
+    module["A4"],
+)
 m_pvspec = pvlib.spectrum.spectral_factor_pvspec(airmass_absolute, kc,
                                                  'multisi')
 m_fs = pvlib.spectrum.spectral_factor_firstsolar(w, airmass_absolute,