restructure pvlib/spectrum (#2136)

* restructure pvlib/spectrum

update __init__.py
rename mismatch.py to spectral_mismatch.py
create spectral_irradiance.py, spectral_response.py

* update irr and mismatch

* update irr mismatch

* Update __init__.py

* Update spectral_mismatch.py

resolve circular imports (attempt)

* Update spectral_mismatch.py

* Update spectral_mismatch.py

* Update v0.11.1.rst

* Update v0.11.1.rst

breaking -> breaking up

* remove spectral  prefix

* update file names

docs/sphinx/source/whatsnew/v0.11.1.rst

@@ -16,7 +16,10 @@ Enhancements
 * Add new parameters for min/max absolute air mass to
   :py:func:`pvlib.spectrum.spectral_factor_firstsolar`.
   (:issue:`2086`, :pull:`2100`)
-
+* Restructured the pvlib/spectrum folder by breaking up the contents of
+  pvlib/spectrum/mismatch.py into pvlib/spectrum/mismatch.py,
+  pvlib/spectrum/irradiance.py, and
+  pvlib/spectrum/response.py. (:issue:`2125`, :pull:`2136`)
 * Added function for calculating wind speed at different heights,
   :py:func:`pvlib.atmosphere.windspeed_powerlaw`.
   (:issue:`2118`, :pull:`2124`)

pvlib/spectrum/__init__.py

@@ -1,14 +1,18 @@
 from pvlib.spectrum.spectrl2 import spectrl2  # noqa: F401
 from pvlib.spectrum.mismatch import (  # noqa: F401
     calc_spectral_mismatch_field,
-    get_am15g,
-    get_reference_spectra,
-    get_example_spectral_response,
     spectral_factor_caballero,
     spectral_factor_firstsolar,
     spectral_factor_sapm,
     spectral_factor_pvspec,
     spectral_factor_jrc,
+)
+from pvlib.spectrum.irradiance import (  # noqa: F401
+    get_am15g,
+    get_reference_spectra,
+)
+from pvlib.spectrum.response import (  # noqa: F401
+    get_example_spectral_response,
     sr_to_qe,
-    qe_to_sr
+    qe_to_sr,
 )

pvlib/spectrum/irradiance.py

@@ -0,0 +1,178 @@
+"""
+The ``irradiance`` module in the ``spectrum`` package provides functions for
+calculations related to spectral irradiance data.
+"""
+
+import pvlib
+from pvlib._deprecation import deprecated
+import numpy as np
+import pandas as pd
+from pathlib import Path
+from functools import partial
+
+
+@deprecated(
+    since="0.11",
+    removal="0.12",
+    name="pvlib.spectrum.get_am15g",
+    alternative="pvlib.spectrum.get_reference_spectra",
+    addendum=(
+        "The new function reads more data. Use it with "
+        + "standard='ASTM G173-03' and extract the 'global' column."
+    ),
+)
+def get_am15g(wavelength=None):
+    r"""
+    Read the ASTM G173-03 AM1.5 global spectrum on a 37-degree tilted surface,
+    optionally interpolated to the specified wavelength(s).
+
+    Global (tilted) irradiance includes direct and diffuse irradiance from sky
+    and ground reflections, and is more formally called hemispherical
+    irradiance (on a tilted surface).  In the context of photovoltaic systems
+    the irradiance on a flat receiver is frequently called plane-of-array (POA)
+    irradiance.
+
+    Parameters
+    ----------
+    wavelength: 1-D sequence of numeric, optional
+        Wavelengths at which the spectrum is interpolated.
+        By default the 2002 wavelengths of the standard are returned. [nm].
+
+    Returns
+    -------
+    am15g: pandas.Series
+        The AM1.5g standard spectrum indexed by ``wavelength``. [W/(m²nm)].
+
+    Notes
+    -----
+    If ``wavelength`` is specified this function uses linear interpolation.
+
+    If the values in ``wavelength`` are too widely spaced, the integral of the
+    spectrum may deviate from the standard value of 1000.37 W/m².
+
+    The values in the data file provided with pvlib-python are copied from an
+    Excel file distributed by NREL, which is found here:
+    https://www.nrel.gov/grid/solar-resource/assets/data/astmg173.xls
+
+    More information about reference spectra is found here:
+    https://www.nrel.gov/grid/solar-resource/spectra-am1.5.html
+
+    See Also
+    --------
+    pvlib.spectrum.get_reference_spectra : reads also the direct and
+      extraterrestrial components of the spectrum.
+
+    References
+    ----------
+    .. [1] ASTM "G173-03 Standard Tables for Reference Solar Spectral
+       Irradiances: Direct Normal and Hemispherical on 37° Tilted Surface."
+    """  # noqa: E501
+    # Contributed by Anton Driesse (@adriesse), PV Performance Labs. Aug. 2022
+    # modified by @echedey-ls, as a wrapper of spectrum.get_reference_spectra
+    standard = get_reference_spectra(wavelength, standard="ASTM G173-03")
+    return standard["global"]
+
+
+def get_reference_spectra(wavelengths=None, standard="ASTM G173-03"):
+    r"""
+    Read a standard spectrum specified by ``standard``, optionally
+    interpolated to the specified wavelength(s).
+
+    Defaults to ``ASTM G173-03`` AM1.5 standard [1]_, which returns
+    ``extraterrestrial``, ``global`` and ``direct`` spectrum on a 37-degree
+    tilted surface, optionally interpolated to the specified wavelength(s).
+
+    Parameters
+    ----------
+    wavelengths : numeric, optional
+        Wavelengths at which the spectrum is interpolated. [nm].
+        If not provided, the original wavelengths from the specified standard
+        are used. Values outside that range are filled with zeros.
+
+    standard : str, default "ASTM G173-03"
+        The reference standard to be read. Only the reference
+        ``"ASTM G173-03"`` is available at the moment.
+
+    Returns
+    -------
+    standard_spectra : pandas.DataFrame
+        The standard spectrum by ``wavelength [nm]``. [W/(m²nm)].
+        Column names are ``extraterrestrial``, ``direct`` and ``global``.
+
+    Notes
+    -----
+    If ``wavelength`` is specified, linear interpolation is used.
+
+    If the values in ``wavelength`` are too widely spaced, the integral of each
+    spectrum may deviate from its standard value.
+    For global spectra, it is about 1000.37 W/m².
+
+    The values of the ASTM G173-03 provided with pvlib-python are copied from
+    an Excel file distributed by NREL, which is found here [2]_:
+    https://www.nrel.gov/grid/solar-resource/assets/data/astmg173.xls
+
+    Examples
+    --------
+    >>> from pvlib import spectrum
+    >>> am15 = spectrum.get_reference_spectra()
+    >>> am15_extraterrestrial, am15_global, am15_direct = \
+    >>>     am15['extraterrestrial'], am15['global'], am15['direct']
+    >>> print(am15.head())
+                extraterrestrial        global        direct
+    wavelength
+    280.0                  0.082  4.730900e-23  2.536100e-26
+    280.5                  0.099  1.230700e-21  1.091700e-24
+    281.0                  0.150  5.689500e-21  6.125300e-24
+    281.5                  0.212  1.566200e-19  2.747900e-22
+    282.0                  0.267  1.194600e-18  2.834600e-21
+
+    >>> am15 = spectrum.get_reference_spectra([300, 500, 800, 1100])
+    >>> print(am15)
+                extraterrestrial   global    direct
+    wavelength
+    300                  0.45794  0.00102  0.000456
+    500                  1.91600  1.54510  1.339100
+    800                  1.12480  1.07250  0.988590
+    1100                 0.60000  0.48577  0.461130
+
+    References
+    ----------
+    .. [1] ASTM "G173-03 Standard Tables for Reference Solar Spectral
+       Irradiances: Direct Normal and Hemispherical on 37° Tilted Surface."
+    .. [2] “Reference Air Mass 1.5 Spectra,” www.nrel.gov.
+       https://www.nrel.gov/grid/solar-resource/spectra-am1.5.html
+    """  # Contributed by Echedey Luis, inspired by Anton Driesse (get_am15g)
+    SPECTRA_FILES = {
+        "ASTM G173-03": "ASTMG173.csv",
+    }
+    pvlib_datapath = Path(pvlib.__path__[0]) / "data"
+
+    try:
+        filepath = pvlib_datapath / SPECTRA_FILES[standard]
+    except KeyError:
+        raise ValueError(
+            f"Invalid standard identifier '{standard}'. Available "
+            + "identifiers are: "
+            + ", ".join(SPECTRA_FILES.keys())
+        )
+
+    standard = pd.read_csv(
+        filepath,
+        header=1,  # expect first line of description, then column names
+        index_col=0,  # first column is "wavelength"
+        dtype=float,
+    )
+
+    if wavelengths is not None:
+        interpolator = partial(
+            np.interp, xp=standard.index, left=0.0, right=0.0
+        )
+        standard = pd.DataFrame(
+            index=wavelengths,
+            data={
+                col: interpolator(x=wavelengths, fp=standard[col])
+                for col in standard.columns
+            },
+        )
+
+    return standard