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fix _delta_kt_prime_dirint end values #638

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Merged
merged 9 commits into from
Jan 9, 2019
Merged

fix _delta_kt_prime_dirint end values #638

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972cffb
fix _delta_kt_prime_dirint end values
cwhanse Jan 3, 2019
9ef66ee
syntax, test fixes:
cwhanse Jan 3, 2019
1f48ee3
syntax and test fixes
cwhanse Jan 4, 2019
c24aca4
more test fixes
cwhanse Jan 4, 2019
ad0e721
more test fixes
cwhanse Jan 4, 2019
7045ff5
and more test fixes
cwhanse Jan 4, 2019
9df2bec
and still more test fixes
cwhanse Jan 4, 2019
fc7eac7
add comments, update whatsnew
cwhanse Jan 4, 2019
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delete space
cwhanse Jan 9, 2019
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2 changes: 2 additions & 0 deletions docs/sphinx/source/whatsnew/v0.6.1.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -73,6 +73,8 @@ Bug fixes
* Fix documentation errors when using IPython >= 7.0.
* Fix error in :func:`pvlib.modelchain.ModelChain.infer_spectral_model` (:issue:`619`)
* Fix error in ``pvlib.spa`` when using Python 3.7 on some platforms.
* Fix error in :func:`pvlib.irradiance._delta_kt_prime_dirint` (:issue: `637`). The error affects
the first and last values of DNI calculated by the function :func:`pvlib.irradiance.dirint`


Testing
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14 changes: 10 additions & 4 deletions pvlib/irradiance.py
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Expand Up @@ -1558,14 +1558,20 @@ def _dirint_from_dni_ktprime(dni, kt_prime, solar_zenith, use_delta_kt_prime,

def _delta_kt_prime_dirint(kt_prime, use_delta_kt_prime, times):
"""
Calculate delta kt prime (Perez eqn 2), or return a default value
Calculate delta_kt_prime (Perez eqn 2 and eqn 3), or return a default value
for use with :py:func:`_dirint_bins`.
"""
if use_delta_kt_prime:
# Perez eqn 2
delta_kt_prime = 0.5*((kt_prime - kt_prime.shift(1)).abs().add(
(kt_prime - kt_prime.shift(-1)).abs(),
fill_value=0))
kt_next = kt_prime.shift(-1)
kt_previous = kt_prime.shift(1)
# replace nan with values that implement Perez Eq 3 for first and last
# positions. Use kt_previous and kt_next to handle series of length 1
kt_next.iloc[-1] = kt_previous.iloc[-1]
kt_previous.iloc[0] = kt_next.iloc[0]
delta_kt_prime = 0.5 * ((kt_prime - kt_next).abs().add(
(kt_prime - kt_previous).abs(),
fill_value=0))
else:
# do not change unless also modifying _dirint_bins
delta_kt_prime = pd.Series(-1, index=times)
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18 changes: 9 additions & 9 deletions pvlib/test/test_irradiance.py
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Expand Up @@ -466,13 +466,13 @@ def test_dirint_value():
pressure = 93193.
dirint_data = irradiance.dirint(ghi, zenith, times, pressure=pressure)
assert_almost_equal(dirint_data.values,
np.array([ 888. , 683.7]), 1)
np.array([868.8, 699.7]), 1)


def test_dirint_nans():
times = pd.DatetimeIndex(start='2014-06-24T12-0700', periods=5, freq='6H')
ghi = pd.Series([np.nan, 1038.62, 1038.62, 1038.62, 1038.62], index=times)
zenith = pd.Series([10.567, np.nan, 10.567, 10.567, 10.567,], index=times)
zenith = pd.Series([10.567, np.nan, 10.567, 10.567, 10.567], index=times)
pressure = pd.Series([93193., 93193., np.nan, 93193., 93193.], index=times)
temp_dew = pd.Series([10, 10, 10, np.nan, 10], index=times)
dirint_data = irradiance.dirint(ghi, zenith, times, pressure=pressure,
Expand All @@ -489,7 +489,7 @@ def test_dirint_tdew():
dirint_data = irradiance.dirint(ghi, zenith, times, pressure=pressure,
temp_dew=10)
assert_almost_equal(dirint_data.values,
np.array([892.9, 636.5]), 1)
np.array([882.1, 672.6]), 1)


def test_dirint_no_delta_kt():
Expand Down Expand Up @@ -559,7 +559,7 @@ def test_gti_dirint():
expected = pd.DataFrame(array(
[[ 21.05796198, 0. , 21.05796198],
[ 288.22574368, 60.59964218, 245.37532576],
[ 930.85454521, 695.8504884 , 276.96897609]]),
[ 931.04078010, 695.94965324, 277.06172442]]),
columns=expected_col_order, index=times)

assert_frame_equal(output, expected)
Expand All @@ -583,7 +583,7 @@ def test_gti_dirint():
expected = pd.DataFrame(array(
[[ 21.05796198, 0. , 21.05796198],
[ 289.81109139, 60.52460392, 247.01373353],
[ 932.22047435, 647.68716072, 323.59362885]]),
[ 932.46756378, 648.05001357, 323.49974813]]),
columns=expected_col_order, index=times)

assert_frame_equal(output, expected)
Expand All @@ -595,9 +595,9 @@ def test_gti_dirint():
albedo=albedo)

expected = pd.DataFrame(array(
[[ 21.3592591 , 0. , 21.3592591 ],
[ 292.5162373 , 64.42628826, 246.95997198],
[ 941.47847463, 727.07261187, 258.25370648]]),
[[ 21.3592591, 0. , 21.3592591 ],
[ 292.5162373, 64.42628826, 246.95997198],
[ 941.6753031, 727.16311901, 258.36548605]]),
columns=expected_col_order, index=times)

assert_frame_equal(output, expected)
Expand All @@ -611,7 +611,7 @@ def test_gti_dirint():
expected = pd.DataFrame(array(
[[ 21.05796198, 0. , 21.05796198],
[ 292.40468994, 36.79559287, 266.3862767 ],
[ 930.72198876, 712.36063132, 261.32196017]]),
[ 931.79627208, 689.81549269, 283.5817439]]),
columns=expected_col_order, index=times)

assert_frame_equal(output, expected)
Expand Down