From 55c95305c63b26b6476f35b1551581332765dd5b Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Fri, 23 Feb 2024 15:01:55 -0700
Subject: [PATCH 01/13] add fit_huld

---
 pvlib/pvarray.py            | 31 +++++++++++++++++++++++++++++++
 pvlib/tests/test_pvarray.py | 15 +++++++++++++++
 2 files changed, 46 insertions(+)

diff --git a/pvlib/pvarray.py b/pvlib/pvarray.py
index a8bbd36eb3..774724f2f3 100644
--- a/pvlib/pvarray.py
+++ b/pvlib/pvarray.py
@@ -11,6 +11,7 @@
 import numpy as np
 from scipy.optimize import curve_fit
 from scipy.special import exp10
+import statsmodels.api as sm
 
 
 def pvefficiency_adr(effective_irradiance, temp_cell,
@@ -348,3 +349,33 @@ def huld(effective_irradiance, temp_mod, pdc0, k=None, cell_type=None):
                     k[2] * tprime + k[3] * tprime * logGprime +
                     k[4] * tprime * logGprime**2 + k[5] * tprime**2)
     return pdc
+
+
+def _build_iec61853():
+    ee = np.array([100, 100, 200, 200, 400, 400, 400, 600, 600, 600, 600,
+                   800, 800, 800, 800, 1000, 1000, 1000, 1000, 1100, 1100,
+                   1100]).T
+    tc = np.array([15, 25, 15, 25, 15, 25, 50, 15, 25, 50, 75,
+                   15, 25, 50, 75, 15, 25, 50, 75, 25, 50, 75]).T
+    return ee, tc
+
+
+def fit_huld(effective_irradiance, temp_mod, pdc):
+    gprime = effective_irradiance / 1000
+    tprime = temp_mod - 25
+    # accomodate gprime<=0
+    with np.errstate(divide='ignore'):
+        logGprime = np.log(gprime, out=np.zeros_like(gprime),
+                           where=np.array(gprime > 0))
+        Y = np.divide(pdc, gprime, out=np.zeros_like(gprime),
+                      where=np.array(gprime > 0))
+    
+    X = np.stack((logGprime, logGprime**2, tprime, tprime*logGprime,
+                  tprime*logGprime**2, tprime**2), axis=0).T
+    X = sm.add_constant(X)
+        
+    rlm_model = sm.RLM(Y, X)
+    rlm_result = rlm_model.fit()
+    pdc0 = rlm_result.params[0]
+    k = rlm_result.params[1:]
+    return pdc0, k
diff --git a/pvlib/tests/test_pvarray.py b/pvlib/tests/test_pvarray.py
index 693ef78b2a..a059373655 100644
--- a/pvlib/tests/test_pvarray.py
+++ b/pvlib/tests/test_pvarray.py
@@ -69,3 +69,18 @@ def test_huld():
     with pytest.raises(ValueError,
                        match='Either k or cell_type must be specified'):
         res = pvarray.huld(1000, 25, 100)
+
+
+def test_fit_huld():
+    # test is to recover the parameters in _infer_huld_k for each cell type
+    # IEC61853 conditions to make data for fitting
+    ee, tc = pvarray._build_iec61853()
+    techs = ['csi', 'cis', 'cdte']
+    pdc0 = 250
+    for tech in techs:
+        k0 = pvarray._infer_k_huld(tech, pdc0)
+        pdc = pvarray.huld(ee, tc, pdc0, cell_type=tech)
+        m_pdc0, k = pvarray.fit_huld(ee, tc, pdc)
+        expected = np.array([pdc0,] + [v for v in k0], dtype=float)
+        modeled = np.hstack((m_pdc0, k))
+        assert_allclose(expected, modeled, rtol=1e-8)

From 119b0b8c5001e6f6ffca3eb87154de27302fec8b Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Fri, 23 Feb 2024 15:04:37 -0700
Subject: [PATCH 02/13] docs

---
 docs/sphinx/source/reference/pv_modeling/system_models.rst | 1 +
 docs/sphinx/source/whatsnew/v0.10.4.rst                    | 1 +
 2 files changed, 2 insertions(+)

diff --git a/docs/sphinx/source/reference/pv_modeling/system_models.rst b/docs/sphinx/source/reference/pv_modeling/system_models.rst
index 55e01f437e..bde7e5808c 100644
--- a/docs/sphinx/source/reference/pv_modeling/system_models.rst
+++ b/docs/sphinx/source/reference/pv_modeling/system_models.rst
@@ -55,3 +55,4 @@ PVGIS model
    :toctree: ../generated/
 
     pvarray.huld
+    pvarray.fit_huld
diff --git a/docs/sphinx/source/whatsnew/v0.10.4.rst b/docs/sphinx/source/whatsnew/v0.10.4.rst
index 997ca4c249..2f0b8bfbbc 100644
--- a/docs/sphinx/source/whatsnew/v0.10.4.rst
+++ b/docs/sphinx/source/whatsnew/v0.10.4.rst
@@ -8,6 +8,7 @@ v0.10.4 (Anticipated March, 2024)
 Enhancements
 ~~~~~~~~~~~~
 * Added the Huld PV model used by PVGIS (:pull:`1940`)
+* Added a method to fit the Huld PV model (:pull:`XXXX`)
 
 
 Bug fixes

From 007cb40305b402e640dffcd71e2b07c2520684ec Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Fri, 23 Feb 2024 15:06:06 -0700
Subject: [PATCH 03/13] Update v0.10.4.rst

---
 docs/sphinx/source/whatsnew/v0.10.4.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/sphinx/source/whatsnew/v0.10.4.rst b/docs/sphinx/source/whatsnew/v0.10.4.rst
index 2f0b8bfbbc..48652da643 100644
--- a/docs/sphinx/source/whatsnew/v0.10.4.rst
+++ b/docs/sphinx/source/whatsnew/v0.10.4.rst
@@ -8,7 +8,7 @@ v0.10.4 (Anticipated March, 2024)
 Enhancements
 ~~~~~~~~~~~~
 * Added the Huld PV model used by PVGIS (:pull:`1940`)
-* Added a method to fit the Huld PV model (:pull:`XXXX`)
+* Added a method to fit the Huld PV model (:pull:`1979`)
 
 
 Bug fixes

From 52c0d42c19ae988c66c8424b329b0de8996208d1 Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Fri, 23 Feb 2024 16:30:58 -0700
Subject: [PATCH 04/13] formatting, mark for scipy

---
 pvlib/pvarray.py            | 4 ++--
 pvlib/tests/test_pvarray.py | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/pvlib/pvarray.py b/pvlib/pvarray.py
index 774724f2f3..38570a806b 100644
--- a/pvlib/pvarray.py
+++ b/pvlib/pvarray.py
@@ -369,11 +369,11 @@ def fit_huld(effective_irradiance, temp_mod, pdc):
                            where=np.array(gprime > 0))
         Y = np.divide(pdc, gprime, out=np.zeros_like(gprime),
                       where=np.array(gprime > 0))
-    
+
     X = np.stack((logGprime, logGprime**2, tprime, tprime*logGprime,
                   tprime*logGprime**2, tprime**2), axis=0).T
     X = sm.add_constant(X)
-        
+
     rlm_model = sm.RLM(Y, X)
     rlm_result = rlm_model.fit()
     pdc0 = rlm_result.params[0]
diff --git a/pvlib/tests/test_pvarray.py b/pvlib/tests/test_pvarray.py
index a059373655..adc4bbb14d 100644
--- a/pvlib/tests/test_pvarray.py
+++ b/pvlib/tests/test_pvarray.py
@@ -3,7 +3,7 @@
 from numpy.testing import assert_allclose
 from .conftest import assert_series_equal
 import pytest
-
+from pvlib.tests.conftest import requires_statsmodels
 from pvlib import pvarray
 
 
@@ -70,7 +70,7 @@ def test_huld():
                        match='Either k or cell_type must be specified'):
         res = pvarray.huld(1000, 25, 100)
 
-
+@requires_statsmodels
 def test_fit_huld():
     # test is to recover the parameters in _infer_huld_k for each cell type
     # IEC61853 conditions to make data for fitting
@@ -81,6 +81,6 @@ def test_fit_huld():
         k0 = pvarray._infer_k_huld(tech, pdc0)
         pdc = pvarray.huld(ee, tc, pdc0, cell_type=tech)
         m_pdc0, k = pvarray.fit_huld(ee, tc, pdc)
-        expected = np.array([pdc0,] + [v for v in k0], dtype=float)
+        expected = np.array([pdc0, ] + [v for v in k0], dtype=float)
         modeled = np.hstack((m_pdc0, k))
         assert_allclose(expected, modeled, rtol=1e-8)

From 0c68e787901d05dd0fbf39fc1de96b3ff4119388 Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Fri, 23 Feb 2024 16:47:24 -0700
Subject: [PATCH 05/13] adjust import, add docstring

---
 pvlib/pvarray.py            | 38 +++++++++++++++++++++++++++++++++++--
 pvlib/tests/test_pvarray.py |  1 +
 2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/pvlib/pvarray.py b/pvlib/pvarray.py
index 38570a806b..645450e418 100644
--- a/pvlib/pvarray.py
+++ b/pvlib/pvarray.py
@@ -11,7 +11,6 @@
 import numpy as np
 from scipy.optimize import curve_fit
 from scipy.special import exp10
-import statsmodels.api as sm
 
 
 def pvefficiency_adr(effective_irradiance, temp_cell,
@@ -270,7 +269,7 @@ def huld(effective_irradiance, temp_mod, pdc0, k=None, cell_type=None):
         Power of the modules at reference conditions 1000 :math:`W/m^2`
         and :math:`25^{\circ}C`. [W]
     k : tuple, optional
-        Empirical coefficients used in the power model. Length 6. If ``k`` is
+        Empirical coefficients used in the Huld model. Length 6. If ``k`` is
         not provided, ``cell_type`` must be specified.
     cell_type : str, optional
         If provided, must be one of ``'cSi'``, ``'CIS'``, or ``'CdTe'``.
@@ -361,6 +360,41 @@ def _build_iec61853():
 
 
 def fit_huld(effective_irradiance, temp_mod, pdc):
+    r'''
+    Fit the Huld model to the input data.
+
+    Parameters
+    ----------
+    effective_irradiance : numeric
+        The irradiance that is converted to photocurrent. [:math:`W/m^2`]
+    temp_mod: numeric
+        Module back-surface temperature. [C]
+    pdc: numeric
+        DC power at ``effectuve_irradiance`` and ``temp_mod``. [W]
+
+    Returns
+    -------
+    pdc0: numeric
+        Power of the modules at reference conditions 1000 :math:`W/m^2`
+        and :math:`25^{\circ}C`. [W]
+    k : tuple
+        Empirical coefficients used in the Huld model. Length 6.
+
+    Notes
+    -----
+    Requires ``statsmodels``.
+
+    See Also
+    --------
+    pvlib.pvarray.huld
+    '''
+
+    try:
+        import statsmodels.api as sm
+    except ImportError:
+        raise ImportError(
+            'fit_huld requires statsmodels')
+
     gprime = effective_irradiance / 1000
     tprime = temp_mod - 25
     # accomodate gprime<=0
diff --git a/pvlib/tests/test_pvarray.py b/pvlib/tests/test_pvarray.py
index adc4bbb14d..83dc90aca0 100644
--- a/pvlib/tests/test_pvarray.py
+++ b/pvlib/tests/test_pvarray.py
@@ -70,6 +70,7 @@ def test_huld():
                        match='Either k or cell_type must be specified'):
         res = pvarray.huld(1000, 25, 100)
 
+
 @requires_statsmodels
 def test_fit_huld():
     # test is to recover the parameters in _infer_huld_k for each cell type

From 7197b8aa8e1831a0b3ee0b49d731124b1a7c5ddf Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Thu, 4 Apr 2024 13:53:12 -0600
Subject: [PATCH 06/13] handle NaN, add note about regression method, use
 temp_module

---
 pvlib/pvarray.py            | 65 ++++++++++++++++++++++++++++---------
 pvlib/tests/test_pvarray.py | 29 +++++++++++++++--
 2 files changed, 77 insertions(+), 17 deletions(-)

diff --git a/pvlib/pvarray.py b/pvlib/pvarray.py
index 645450e418..85ca736043 100644
--- a/pvlib/pvarray.py
+++ b/pvlib/pvarray.py
@@ -242,7 +242,7 @@ def _infer_k_huld(cell_type, pdc0):
     return k
 
 
-def huld(effective_irradiance, temp_mod, pdc0, k=None, cell_type=None):
+def huld(effective_irradiance, temp_module, pdc0, k=None, cell_type=None):
     r"""
     Power (DC) using the Huld model.
 
@@ -263,7 +263,7 @@ def huld(effective_irradiance, temp_mod, pdc0, k=None, cell_type=None):
     ----------
     effective_irradiance : numeric
         The irradiance that is converted to photocurrent. [:math:`W/m^2`]
-    temp_mod: numeric
+    temp_module: numeric
         Module back-surface temperature. [C]
     pdc0: numeric
         Power of the modules at reference conditions 1000 :math:`W/m^2`
@@ -330,6 +330,10 @@ def huld(effective_irradiance, temp_mod, pdc0, k=None, cell_type=None):
            E. Dunlop. A power-rating model for crystalline silicon PV modules.
            Solar Energy Materials and Solar Cells 95, (2011), pp. 3359-3369.
            :doi:`10.1016/j.solmat.2011.07.026`.
+
+    See Also
+    --------
+    pvlib.pvarray.fit_huld
     """
     if k is None:
         if cell_type is not None:
@@ -338,7 +342,7 @@ def huld(effective_irradiance, temp_mod, pdc0, k=None, cell_type=None):
             raise ValueError('Either k or cell_type must be specified')
 
     gprime = effective_irradiance / 1000
-    tprime = temp_mod - 25
+    tprime = temp_module - 25
     # accomodate gprime<=0
     with np.errstate(divide='ignore'):
         logGprime = np.log(gprime, out=np.zeros_like(gprime),
@@ -353,24 +357,27 @@ def huld(effective_irradiance, temp_mod, pdc0, k=None, cell_type=None):
 def _build_iec61853():
     ee = np.array([100, 100, 200, 200, 400, 400, 400, 600, 600, 600, 600,
                    800, 800, 800, 800, 1000, 1000, 1000, 1000, 1100, 1100,
-                   1100]).T
+                   1100], dtype=np.float64).T
     tc = np.array([15, 25, 15, 25, 15, 25, 50, 15, 25, 50, 75,
-                   15, 25, 50, 75, 15, 25, 50, 75, 25, 50, 75]).T
+                   15, 25, 50, 75, 15, 25, 50, 75, 25, 50, 75],
+                  dtype=np.float64).T
     return ee, tc
 
 
-def fit_huld(effective_irradiance, temp_mod, pdc):
+def fit_huld(effective_irradiance, temp_module, pdc, method='ols'):
     r'''
     Fit the Huld model to the input data.
 
     Parameters
     ----------
-    effective_irradiance : numeric
+    effective_irradiance : array-like
         The irradiance that is converted to photocurrent. [:math:`W/m^2`]
-    temp_mod: numeric
+    temp_module: array-like
         Module back-surface temperature. [C]
-    pdc: numeric
-        DC power at ``effectuve_irradiance`` and ``temp_mod``. [W]
+    pdc: array-like
+        DC power at ``effective_irradiance`` and ``temp_module``. [W]
+    method : string, default 'ols'
+        The regression method. Must be either ``'ols'`` or ``'robust'``.
 
     Returns
     -------
@@ -384,6 +391,28 @@ def fit_huld(effective_irradiance, temp_mod, pdc):
     -----
     Requires ``statsmodels``.
 
+    Input data ``effective_irradiance``, ``temp_module`` and ``pdc`` must be
+    equal length. Data are aligned as columns and any row with a NaN in any
+    column is dropped. Remaining data must be at least length 7.
+
+    Huld [1]_ describes fitting by least-squares but doesn't detail the
+    procedure, although it is reasonable that ordinary least-squares regression
+    was used. Ordinary least-squares regression can be unduly influenced by
+    data points with large deviations from the mean of the dependent variable
+    ``pdc``. For example, these data may occur when short-duration shading is
+    present. If filtering is applied to exclude such data, a suitable model
+    can be obtained with ordinary least-squares regression. As an alternative,
+    this function also provides a 'robust' regression option (an iteratively
+    reweighted least-squares method) that is more tolerant of outliers in the
+    dependent variable.
+
+    References
+    ----------
+    .. [1] T. Huld, G. Friesen, A. Skoczek, R. Kenny, T. Sample, M. Field,
+           E. Dunlop. A power-rating model for crystalline silicon PV modules.
+           Solar Energy Materials and Solar Cells 95, (2011), pp. 3359-3369.
+           :doi:`10.1016/j.solmat.2011.07.026`.
+
     See Also
     --------
     pvlib.pvarray.huld
@@ -396,7 +425,7 @@ def fit_huld(effective_irradiance, temp_mod, pdc):
             'fit_huld requires statsmodels')
 
     gprime = effective_irradiance / 1000
-    tprime = temp_mod - 25
+    tprime = temp_module - 25
     # accomodate gprime<=0
     with np.errstate(divide='ignore'):
         logGprime = np.log(gprime, out=np.zeros_like(gprime),
@@ -408,8 +437,14 @@ def fit_huld(effective_irradiance, temp_mod, pdc):
                   tprime*logGprime**2, tprime**2), axis=0).T
     X = sm.add_constant(X)
 
-    rlm_model = sm.RLM(Y, X)
-    rlm_result = rlm_model.fit()
-    pdc0 = rlm_result.params[0]
-    k = rlm_result.params[1:]
+    if method=='ols':
+        model = sm.OLS(Y, X, missing='drop')
+    elif method=='robust':
+        model = sm.RLM(Y, X, missing='drop')
+    else:
+        raise ValueError("method must be ols or robust")
+
+    result = model.fit()
+    pdc0 = result.params[0]
+    k = result.params[1:]
     return pdc0, k
diff --git a/pvlib/tests/test_pvarray.py b/pvlib/tests/test_pvarray.py
index 83dc90aca0..c569c819a8 100644
--- a/pvlib/tests/test_pvarray.py
+++ b/pvlib/tests/test_pvarray.py
@@ -71,8 +71,9 @@ def test_huld():
         res = pvarray.huld(1000, 25, 100)
 
 
+@pytest.mark.parametrize('method', ['ols', 'robust'])
 @requires_statsmodels
-def test_fit_huld():
+def test_fit_huld(method):
     # test is to recover the parameters in _infer_huld_k for each cell type
     # IEC61853 conditions to make data for fitting
     ee, tc = pvarray._build_iec61853()
@@ -81,7 +82,31 @@ def test_fit_huld():
     for tech in techs:
         k0 = pvarray._infer_k_huld(tech, pdc0)
         pdc = pvarray.huld(ee, tc, pdc0, cell_type=tech)
-        m_pdc0, k = pvarray.fit_huld(ee, tc, pdc)
+        m_pdc0, k = pvarray.fit_huld(ee, tc, pdc, method=method)
         expected = np.array([pdc0, ] + [v for v in k0], dtype=float)
         modeled = np.hstack((m_pdc0, k))
         assert_allclose(expected, modeled, rtol=1e-8)
+    # once more to check that NaNs are handled
+    ee[7] = np.nan
+    tc[9] = np.nan
+    k0 = pvarray._infer_k_huld('csi', pdc0)
+    pdc = pvarray.huld(ee, tc, pdc0, cell_type='csi')
+    pdc[11] = np.nan
+    m_pdc0, k = pvarray.fit_huld(ee, tc, pdc, method='ols')
+    expected = np.array([2.07118648e+02, -8.35033390e+01, -3.83844606e+01,
+                         2.75629738e+00,  1.87571414e+00, -2.86429730e-01,
+                         -6.00418853e-02])
+    modeled = np.hstack((m_pdc0, k))
+    assert_allclose(expected, modeled, rtol=1e-5)
+
+
+@requires_statsmodels
+def test_fit_huld_method_error():
+    # test is to recover the parameters in _infer_huld_k for each cell type
+    # IEC61853 conditions to make data for fitting
+    ee, tc = pvarray._build_iec61853()
+    pdc0 = 250
+    pdc = pvarray.huld(ee, tc, pdc0, cell_type='csi')
+    method='brute_force'
+    with pytest.raises(ValueError, match="method must be ols or robust"):
+        m_pdc0, k = pvarray.fit_huld(ee, tc, pdc, method=method)

From c24b7cc47f2c3d6c89be80e0c3207636da15c4bf Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Thu, 4 Apr 2024 13:53:47 -0600
Subject: [PATCH 07/13] forgot to save

---
 pvlib/tests/test_pvarray.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/pvlib/tests/test_pvarray.py b/pvlib/tests/test_pvarray.py
index c569c819a8..4b5a1aead2 100644
--- a/pvlib/tests/test_pvarray.py
+++ b/pvlib/tests/test_pvarray.py
@@ -93,6 +93,7 @@ def test_fit_huld(method):
     pdc = pvarray.huld(ee, tc, pdc0, cell_type='csi')
     pdc[11] = np.nan
     m_pdc0, k = pvarray.fit_huld(ee, tc, pdc, method='ols')
+    # known solution for OLS obtained with statsmodels v0.14.0
     expected = np.array([2.07118648e+02, -8.35033390e+01, -3.83844606e+01,
                          2.75629738e+00,  1.87571414e+00, -2.86429730e-01,
                          -6.00418853e-02])

From 1250bcd01f54276f14be1ae04f2864f6373f8c9b Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Thu, 4 Apr 2024 14:09:02 -0600
Subject: [PATCH 08/13] lint

---
 pvlib/pvarray.py            | 4 ++--
 pvlib/tests/test_pvarray.py | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/pvlib/pvarray.py b/pvlib/pvarray.py
index 85ca736043..0966c5b5b1 100644
--- a/pvlib/pvarray.py
+++ b/pvlib/pvarray.py
@@ -437,9 +437,9 @@ def fit_huld(effective_irradiance, temp_module, pdc, method='ols'):
                   tprime*logGprime**2, tprime**2), axis=0).T
     X = sm.add_constant(X)
 
-    if method=='ols':
+    if method == 'ols':
         model = sm.OLS(Y, X, missing='drop')
-    elif method=='robust':
+    elif method == 'robust':
         model = sm.RLM(Y, X, missing='drop')
     else:
         raise ValueError("method must be ols or robust")
diff --git a/pvlib/tests/test_pvarray.py b/pvlib/tests/test_pvarray.py
index 4b5a1aead2..c165199729 100644
--- a/pvlib/tests/test_pvarray.py
+++ b/pvlib/tests/test_pvarray.py
@@ -108,6 +108,6 @@ def test_fit_huld_method_error():
     ee, tc = pvarray._build_iec61853()
     pdc0 = 250
     pdc = pvarray.huld(ee, tc, pdc0, cell_type='csi')
-    method='brute_force'
+    method = 'brute_force'
     with pytest.raises(ValueError, match="method must be ols or robust"):
         m_pdc0, k = pvarray.fit_huld(ee, tc, pdc, method=method)

From 464749e5d928149886854109f0bf838fa25c852b Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Thu, 18 Apr 2024 14:51:53 -0600
Subject: [PATCH 09/13] respond to comments

---
 docs/sphinx/source/whatsnew/v0.10.4.rst | 71 -------------------------
 docs/sphinx/source/whatsnew/v0.10.5.rst |  2 +-
 pvlib/pvarray.py                        |  6 +--
 pvlib/tests/test_pvarray.py             |  9 +---
 4 files changed, 6 insertions(+), 82 deletions(-)
 delete mode 100644 docs/sphinx/source/whatsnew/v0.10.4.rst

diff --git a/docs/sphinx/source/whatsnew/v0.10.4.rst b/docs/sphinx/source/whatsnew/v0.10.4.rst
deleted file mode 100644
index 40ccd25b20..0000000000
--- a/docs/sphinx/source/whatsnew/v0.10.4.rst
+++ /dev/null
@@ -1,71 +0,0 @@
-.. _whatsnew_01040:
-
-
-v0.10.4 (March 19, 2024)
-------------------------
-
-
-Enhancements
-~~~~~~~~~~~~
-* Added the Huld PV model used by PVGIS (:pull:`1940`)
-* Added a method to fit the Huld PV model (:pull:`1979`)
-* Add :py:func:`~pvlib.iotools.get_solargis` for retrieving Solargis
-  irradiance data. (:pull:`1969`)
-* Added function :py:func:`pvlib.shading.projected_solar_zenith_angle`,
-  a common calculation in shading and tracking. (:issue:`1734`, :pull:`1904`)
-* Added :py:func:`~pvlib.iotools.get_solrad` for fetching irradiance data from
-  the SOLRAD ground station network. (:pull:`1967`)
-* Added metadata parsing to :py:func:`~pvlib.iotools.read_solrad` to follow the standard iotools
-  convention of returning a tuple of (data, meta). Previously the function only returned a dataframe. (:pull:`1968`)
-
-
-Bug fixes
-~~~~~~~~~
-* Fixed an error in solar position calculations when using
-  :py:class:`pandas.DatetimeIndex` with ``unit`` other than ``'ns'`` (:issue:`1932`).
-  The following functions were affected:
-
-  - :py:class:`~pvlib.modelchain.ModelChain` and :py:func:`~pvlib.solarposition.get_solarposition` with the ``nrel_numpy`` and ``nrel_numba`` methods
-  - :py:func:`~pvlib.solarposition.spa_python`
-  - :py:func:`~pvlib.solarposition.sun_rise_set_transit_spa`
-  - :py:func:`~pvlib.solarposition.nrel_earthsun_distance`
-  - :py:func:`~pvlib.solarposition.hour_angle`
-  - :py:func:`~pvlib.solarposition.sun_rise_set_transit_geometric`
-
-* :py:class:`~pvlib.modelchain.ModelChain` now raises a more useful error when
-  ``temperature_model_parameters`` are specified on the passed ``system`` instead of on its ``arrays``. (:issue:`1759`).
-* :py:func:`pvlib.irradiance.ghi_from_poa_driesse_2023` now correctly makes use
-  of the ``xtol`` argument. Previously, it was ignored. (:issue:`1970`, :pull:`1971`)
-* Fixed incorrect unit conversion of precipitable water used for the Solcast iotools functions. (:pull:`1969`)
-* :py:class:`~pvlib.modelchain.ModelChain.infer_temperature_model` now raises a more useful error when
-  the temperature model cannot be inferred (:issue:`1946`)
-* The default URL for retrieving irradiance data from the SRML network was updated in
-  :py:func:`~pvlib.iotools.get_srml` (:pull:`1957`, :issue:`1922`)
-
-
-Documentation
-~~~~~~~~~~~~~
-* Improved references and description for :py:func:`~pvlib.irradiance.get_ground_diffuse`. (:pull:`1883`, :pull:`1953`)
-* Fixed broken URLs in various places. (:pull:`1957`, :pull:`1960`)
-* Added a gallery example with a model for OEDI system 9068. (:pull:`1985`)
-
-
-Requirements
-~~~~~~~~~~~~
-* Minimum version of pandas advanced from 0.25.0 to 1.3.0. (:pull:`1969`)
-* Minimum version of numpy advanced from 1.16.0 to 1.17.3. (:pull:`1969`)
-
-
-Contributors
-~~~~~~~~~~~~
-* Patrick Sheehan (:ghuser:`patricksheehan`)
-* Echedey Luis (:ghuser:`echedey-ls`)
-* Kevin Anderson (:ghuser:`kandersolar`)
-* Cliff Hansen (:ghuser:`cwhanse`)
-* Roma Koulikov (:ghuser:`matsuobasho`)
-* Adam R. Jensen (:ghuser:`AdamRJensen`)
-* Peter Dudfield (:ghuser:`peterdudfield`)
-* Anton Driesse (:ghuser:`adriesse`)
-* Mark Mikofski (:ghuser:`mikofski`)
-* Will Holmgren (:ghuser:`wholmgren`)
-* Jules Chéron (:ghuser:`jules-ch`)
diff --git a/docs/sphinx/source/whatsnew/v0.10.5.rst b/docs/sphinx/source/whatsnew/v0.10.5.rst
index fe64879c8a..e2378cf615 100644
--- a/docs/sphinx/source/whatsnew/v0.10.5.rst
+++ b/docs/sphinx/source/whatsnew/v0.10.5.rst
@@ -11,7 +11,7 @@ Deprecations
 
 Enhancements
 ~~~~~~~~~~~~
-
+* Added a method to fit the Huld PV model (:pull:`1979`)
 
 Bug fixes
 ~~~~~~~~~
diff --git a/pvlib/pvarray.py b/pvlib/pvarray.py
index 0966c5b5b1..21c23a5a80 100644
--- a/pvlib/pvarray.py
+++ b/pvlib/pvarray.py
@@ -427,10 +427,10 @@ def fit_huld(effective_irradiance, temp_module, pdc, method='ols'):
     gprime = effective_irradiance / 1000
     tprime = temp_module - 25
     # accomodate gprime<=0
+    logGprime = np.log(gprime, out=np.nan*gprime,
+                       where=np.array(gprime > 0))
     with np.errstate(divide='ignore'):
-        logGprime = np.log(gprime, out=np.zeros_like(gprime),
-                           where=np.array(gprime > 0))
-        Y = np.divide(pdc, gprime, out=np.zeros_like(gprime),
+        Y = np.divide(pdc, gprime, out=np.nan*gprime,
                       where=np.array(gprime > 0))
 
     X = np.stack((logGprime, logGprime**2, tprime, tprime*logGprime,
diff --git a/pvlib/tests/test_pvarray.py b/pvlib/tests/test_pvarray.py
index c165199729..309c492c53 100644
--- a/pvlib/tests/test_pvarray.py
+++ b/pvlib/tests/test_pvarray.py
@@ -93,18 +93,13 @@ def test_fit_huld(method):
     pdc = pvarray.huld(ee, tc, pdc0, cell_type='csi')
     pdc[11] = np.nan
     m_pdc0, k = pvarray.fit_huld(ee, tc, pdc, method='ols')
-    # known solution for OLS obtained with statsmodels v0.14.0
-    expected = np.array([2.07118648e+02, -8.35033390e+01, -3.83844606e+01,
-                         2.75629738e+00,  1.87571414e+00, -2.86429730e-01,
-                         -6.00418853e-02])
+    expected = np.array([pdc0, ] + [v for v in k0], dtype=float)
     modeled = np.hstack((m_pdc0, k))
-    assert_allclose(expected, modeled, rtol=1e-5)
+    assert_allclose(expected, modeled, rtol=1e-8)
 
 
 @requires_statsmodels
 def test_fit_huld_method_error():
-    # test is to recover the parameters in _infer_huld_k for each cell type
-    # IEC61853 conditions to make data for fitting
     ee, tc = pvarray._build_iec61853()
     pdc0 = 250
     pdc = pvarray.huld(ee, tc, pdc0, cell_type='csi')

From e0e637e4dd10e486cc5bccf146d4c980408e4b0c Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Thu, 18 Apr 2024 14:55:43 -0600
Subject: [PATCH 10/13] put v0.10.4.rst back

---
 docs/sphinx/source/whatsnew/v0.10.4.rst | 70 +++++++++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100644 docs/sphinx/source/whatsnew/v0.10.4.rst

diff --git a/docs/sphinx/source/whatsnew/v0.10.4.rst b/docs/sphinx/source/whatsnew/v0.10.4.rst
new file mode 100644
index 0000000000..a194c5e522
--- /dev/null
+++ b/docs/sphinx/source/whatsnew/v0.10.4.rst
@@ -0,0 +1,70 @@
+.. _whatsnew_01040:
+
+
+v0.10.4 (March 19, 2024)
+------------------------
+
+
+Enhancements
+~~~~~~~~~~~~
+* Added the Huld PV model used by PVGIS (:pull:`1940`)
+* Add :py:func:`~pvlib.iotools.get_solargis` for retrieving Solargis
+  irradiance data. (:pull:`1969`)
+* Added function :py:func:`pvlib.shading.projected_solar_zenith_angle`,
+  a common calculation in shading and tracking. (:issue:`1734`, :pull:`1904`)
+* Added :py:func:`~pvlib.iotools.get_solrad` for fetching irradiance data from
+  the SOLRAD ground station network. (:pull:`1967`)
+* Added metadata parsing to :py:func:`~pvlib.iotools.read_solrad` to follow the standard iotools
+  convention of returning a tuple of (data, meta). Previously the function only returned a dataframe. (:pull:`1968`)
+
+
+Bug fixes
+~~~~~~~~~
+* Fixed an error in solar position calculations when using
+  :py:class:`pandas.DatetimeIndex` with ``unit`` other than ``'ns'`` (:issue:`1932`).
+  The following functions were affected:
+
+  - :py:class:`~pvlib.modelchain.ModelChain` and :py:func:`~pvlib.solarposition.get_solarposition` with the ``nrel_numpy`` and ``nrel_numba`` methods
+  - :py:func:`~pvlib.solarposition.spa_python`
+  - :py:func:`~pvlib.solarposition.sun_rise_set_transit_spa`
+  - :py:func:`~pvlib.solarposition.nrel_earthsun_distance`
+  - :py:func:`~pvlib.solarposition.hour_angle`
+  - :py:func:`~pvlib.solarposition.sun_rise_set_transit_geometric`
+
+* :py:class:`~pvlib.modelchain.ModelChain` now raises a more useful error when
+  ``temperature_model_parameters`` are specified on the passed ``system`` instead of on its ``arrays``. (:issue:`1759`).
+* :py:func:`pvlib.irradiance.ghi_from_poa_driesse_2023` now correctly makes use
+  of the ``xtol`` argument. Previously, it was ignored. (:issue:`1970`, :pull:`1971`)
+* Fixed incorrect unit conversion of precipitable water used for the Solcast iotools functions. (:pull:`1969`)
+* :py:class:`~pvlib.modelchain.ModelChain.infer_temperature_model` now raises a more useful error when
+  the temperature model cannot be inferred (:issue:`1946`)
+* The default URL for retrieving irradiance data from the SRML network was updated in
+  :py:func:`~pvlib.iotools.get_srml` (:pull:`1957`, :issue:`1922`)
+
+
+Documentation
+~~~~~~~~~~~~~
+* Improved references and description for :py:func:`~pvlib.irradiance.get_ground_diffuse`. (:pull:`1883`, :pull:`1953`)
+* Fixed broken URLs in various places. (:pull:`1957`, :pull:`1960`)
+* Added a gallery example with a model for OEDI system 9068. (:pull:`1985`)
+
+
+Requirements
+~~~~~~~~~~~~
+* Minimum version of pandas advanced from 0.25.0 to 1.3.0. (:pull:`1969`)
+* Minimum version of numpy advanced from 1.16.0 to 1.17.3. (:pull:`1969`)
+
+
+Contributors
+~~~~~~~~~~~~
+* Patrick Sheehan (:ghuser:`patricksheehan`)
+* Echedey Luis (:ghuser:`echedey-ls`)
+* Kevin Anderson (:ghuser:`kandersolar`)
+* Cliff Hansen (:ghuser:`cwhanse`)
+* Roma Koulikov (:ghuser:`matsuobasho`)
+* Adam R. Jensen (:ghuser:`AdamRJensen`)
+* Peter Dudfield (:ghuser:`peterdudfield`)
+* Anton Driesse (:ghuser:`adriesse`)
+* Mark Mikofski (:ghuser:`mikofski`)
+* Will Holmgren (:ghuser:`wholmgren`)
+* Jules Chéron (:ghuser:`jules-ch`)

From 1305f6e710fb383983d6e5011134d5fab10955a2 Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Fri, 31 May 2024 11:04:13 -0700
Subject: [PATCH 11/13] move to v0.11.0

---
 docs/sphinx/source/whatsnew/v0.11.0.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/sphinx/source/whatsnew/v0.11.0.rst b/docs/sphinx/source/whatsnew/v0.11.0.rst
index 22d6046774..09d97a49ce 100644
--- a/docs/sphinx/source/whatsnew/v0.11.0.rst
+++ b/docs/sphinx/source/whatsnew/v0.11.0.rst
@@ -21,7 +21,7 @@ Enhancements
   shade perpendicular to ``axis_azimuth``. The function is applicable to both
   fixed-tilt and one-axis tracking systems.
   (:issue:`1689`, :pull:`1725`, :pull:`1962`)
-
+* Added a method to fit the Huld PV model (:pull:`1979`)
 
 Bug fixes
 ~~~~~~~~~

From e1873fc5afca6fc6cb944917dc9413c80bef718a Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Fri, 31 May 2024 11:05:16 -0700
Subject: [PATCH 12/13] restore v0.10.5 whatsnew

---
 docs/sphinx/source/whatsnew/v0.10.5.rst | 11 -----------
 1 file changed, 11 deletions(-)

diff --git a/docs/sphinx/source/whatsnew/v0.10.5.rst b/docs/sphinx/source/whatsnew/v0.10.5.rst
index 77dad0dc19..00daed3a0f 100644
--- a/docs/sphinx/source/whatsnew/v0.10.5.rst
+++ b/docs/sphinx/source/whatsnew/v0.10.5.rst
@@ -1,17 +1,6 @@
 .. _whatsnew_01050:
 
 
-v0.10.5 (Anticipated June 2024)
--------------------------------
-
-
-Deprecations
-~~~~~~~~~~~~
-
-
-Enhancements
-~~~~~~~~~~~~
-* Added a method to fit the Huld PV model (:pull:`1979`)
 v0.10.5 (May 6, 2024)
 ---------------------
 

From 6437c14b9043883b96be9bfcba75133de686376d Mon Sep 17 00:00:00 2001
From: Cliff Hansen <cwhanse@sandia.gov>
Date: Fri, 31 May 2024 11:08:43 -0700
Subject: [PATCH 13/13] Update v0.11.0.rst

---
 docs/sphinx/source/whatsnew/v0.11.0.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/docs/sphinx/source/whatsnew/v0.11.0.rst b/docs/sphinx/source/whatsnew/v0.11.0.rst
index 09d97a49ce..cbf9c35bd9 100644
--- a/docs/sphinx/source/whatsnew/v0.11.0.rst
+++ b/docs/sphinx/source/whatsnew/v0.11.0.rst
@@ -9,6 +9,7 @@ Breaking changes
 ~~~~~~~~~~~~~~~~
 * The deprecated ``pvlib.modelchain.basic_chain`` has now been removed. (:pull:`1862`)
 * Remove the `poa_horizontal_ratio` function and all of its references. (:issue:`1697`, :pull:`2021`)
+* Parameter ``temp_mod`` in :py:func:`pvlib.pvarray.huld` is renamed to ``temp_module``. (:pull:`1979`)
 
 
 Deprecations