From c8c3758525a376846244ace0c79e7efd7ac54e3e Mon Sep 17 00:00:00 2001
From: Joshua Stein <jsstein@sandia.gov>
Date: Wed, 20 May 2020 16:34:20 -0600
Subject: [PATCH 01/27] bug fixes to hsu soiling function.  Addresses (#970)

---
 pvlib/soiling.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/pvlib/soiling.py b/pvlib/soiling.py
index 1b7aadc73d..0bdc6228a5 100644
--- a/pvlib/soiling.py
+++ b/pvlib/soiling.py
@@ -40,7 +40,7 @@ def hsu(rainfall, cleaning_threshold, tilt, pm2_5, pm10,
         Concentration of airborne particulate matter (PM) with
         aerodynamicdiameter less than 10 microns. [g/m^3]
 
-    depo_veloc : dict, default {'2_5': 0.4, '10': 0.09}
+    depo_veloc : dict, default {'2_5': 0.0009, '10': 0.004}
         Deposition or settling velocity of particulates. [m/s]
 
     rain_accum_period : Timedelta, default 1 hour
@@ -69,7 +69,7 @@ def hsu(rainfall, cleaning_threshold, tilt, pm2_5, pm10,
 
     # never use mutable input arguments
     if depo_veloc is None:
-        depo_veloc = {'2_5': 0.004, '10': 0.0009}
+        depo_veloc = {'2_5': 0.0009, '10': 0.004}
 
     # accumulate rainfall into periods for comparison with threshold
     accum_rain = rainfall.rolling(rain_accum_period, closed='right').sum()
@@ -77,7 +77,7 @@ def hsu(rainfall, cleaning_threshold, tilt, pm2_5, pm10,
     cleaning_times = accum_rain.index[accum_rain >= cleaning_threshold]
 
     horiz_mass_rate = pm2_5 * depo_veloc['2_5']\
-        + np.maximum(pm10 - pm2_5, 0.) * depo_veloc['10']
+        + np.maximum(pm10 - pm2_5, 0.) * depo_veloc['10'] * 3600
     tilted_mass_rate = horiz_mass_rate * cosd(tilt)  # assuming no rain
 
     # tms -> tilt_mass_rate

From 3a77400c8fd7c6912741ea7db80c5733ef9b9523 Mon Sep 17 00:00:00 2001
From: Joshua Stein <jsstein@sandia.gov>
Date: Tue, 9 Jun 2020 11:28:11 -0600
Subject: [PATCH 02/27] Made changes to the soiling tests Addresses (#970)

---
 pvlib/tests/test_soiling.py | 67 ++++++++++++++++---------------------
 1 file changed, 29 insertions(+), 38 deletions(-)

diff --git a/pvlib/tests/test_soiling.py b/pvlib/tests/test_soiling.py
index b80dd13547..eafe11ddf5 100644
--- a/pvlib/tests/test_soiling.py
+++ b/pvlib/tests/test_soiling.py
@@ -19,48 +19,40 @@ def expected_output():
                        end=pd.Timestamp(2019, 1, 1, 23, 59, 0), freq='1h')
 
     expected_no_cleaning = pd.Series(
-        data=[0.884980357535360, 0.806308930084762, 0.749974647038078,
-              0.711804155175089, 0.687489866078621, 0.672927554408964,
-              0.664714899337491, 0.660345851212099, 0.658149551658860,
-              0.657104593968981, 0.656633344364056, 0.656431630729954,
-              0.656349579062171, 0.656317825078228, 0.656306121502393,
-              0.656302009396500, 0.656300630853678, 0.656300189543417,
-              0.656300054532516, 0.656300015031680, 0.656300003971846,
-              0.656300001006533, 0.656300000244750, 0.656300000057132],
+        data=[0.97230454, 0.95036146, 0.93039061, 0.91177978, 0.89427556,
+              0.8777455 , 0.86211038, 0.84731759, 0.83332881, 0.82011354,
+              0.80764549, 0.79590056, 0.78485556, 0.77448749, 0.76477312,
+              0.75568883, 0.74721046, 0.73931338, 0.73197253, 0.72516253,
+              0.7188578 , 0.71303268, 0.7076616 , 0.70271919],
         index=dt)
-
     return expected_no_cleaning
 
-
 @pytest.fixture
 def expected_output_1():
-    return np.array([
-        0.99927224, 0.99869067, 0.99815393, 0.99764437, 1.0,
-        0.99927224, 0.99869067, 0.99815393, 1.0, 1.0,
-        0.99927224, 0.99869067, 0.99815393, 0.99764437, 0.99715412,
-        0.99667873, 0.99621536, 0.99576203, 0.99531731, 0.9948801,
-        0.99444954, 0.99402494, 0.99360572, 0.99319142])
-
+    dt = pd.date_range(start=pd.Timestamp(2019, 1, 1, 0, 0, 0),
+        end=pd.Timestamp(2019, 1, 1, 23, 59, 0), freq='1h')
+    expected_output_1 = pd.Series(
+        data=[0.9872406 , 0.97706269, 0.96769693, 0.95884032, 1.,
+              0.9872406 , 0.97706269, 0.96769693, 1.        , 1.        ,
+              0.9872406 , 0.97706269, 0.96769693, 0.95884032, 0.95036001,
+              0.94218263, 0.93426236, 0.92656836, 0.91907873, 0.91177728,
+              0.9046517 , 0.89769238, 0.89089165, 0.88424329],
+        index=dt)
+    return expected_output_1
 
 @pytest.fixture
-def expected_output_2(expected_output):
-    # Sample output (calculated manually)
+def expected_output_2():
     dt = pd.date_range(start=pd.Timestamp(2019, 1, 1, 0, 0, 0),
                        end=pd.Timestamp(2019, 1, 1, 23, 59, 0), freq='1h')
+    expected_output_2 = pd.Series(  
+            data = [0.97229869, 0.95035106, 0.93037619, 0.91176175, 1.,
+            1.        , 1.        , 0.97229869, 1.        , 1.        ,
+            1.        , 1.        , 0.97229869, 0.95035106, 0.93037619,
+            0.91176175, 0.89425431, 1.        , 1.        , 1.        ,
+            1.        , 0.97229869, 0.95035106, 0.93037619],
+        index=dt)
 
-    expected_no_cleaning = expected_output
-
-    expected = pd.Series(index=dt, dtype='float64')
-    expected[dt[:4]] = expected_no_cleaning[dt[:4]]
-    expected[dt[4:7]] = 1.
-    expected[dt[7]] = expected_no_cleaning[dt[0]]
-    expected[dt[8:12]] = 1.
-    expected[dt[12:17]] = expected_no_cleaning[dt[:5]]
-    expected[dt[17:21]] = 1.
-    expected[dt[21:]] = expected_no_cleaning[:3]
-
-    return expected
-
+    return expected_output_2
 
 @pytest.fixture
 def rainfall_input():
@@ -81,7 +73,7 @@ def test_hsu_no_cleaning(rainfall_input, expected_output):
     rainfall = rainfall_input
     pm2_5 = 1.0
     pm10 = 2.0
-    depo_veloc = {'2_5': 1.0, '10': 1.0}
+    depo_veloc = {'2_5': 1.0e-5, '10': 1.0e-4}
     tilt = 0.
     expected_no_cleaning = expected_output
 
@@ -99,16 +91,15 @@ def test_hsu(rainfall_input, expected_output_2):
     rainfall = rainfall_input
     pm2_5 = 1.0
     pm10 = 2.0
-    depo_veloc = {'2_5': 1.0, '10': 1.0}
+    depo_veloc = {'2_5': 1.0e-4, '10': 1.0e-4}
     tilt = 0.
-    expected = expected_output_2
 
     # three cleaning events at 4:00-6:00, 8:00-11:00, and 17:00-20:00
     result = hsu(rainfall=rainfall, cleaning_threshold=0.5, tilt=tilt,
                  pm2_5=pm2_5, pm10=pm10, depo_veloc=depo_veloc,
                  rain_accum_period=pd.Timedelta('3h'))
 
-    assert_series_equal(result, expected)
+    assert_series_equal(result, expected_output_2)
 
 
 @requires_scipy
@@ -119,8 +110,8 @@ def test_hsu_defaults(rainfall_input, expected_output_1):
     accumulation period.
     """
     result = hsu(
-        rainfall=rainfall_input, cleaning_threshold=0.5, tilt=0.0, pm2_5=1.0,
-        pm10=2.0)
+        rainfall=rainfall_input, cleaning_threshold=0.5, tilt=0.0, pm2_5=1.0e-2,
+        pm10=2.0e-2)
     assert np.allclose(result.values, expected_output_1)
 
 

From bff444f6cb059ed37775e40a33f50d730b55e50d Mon Sep 17 00:00:00 2001
From: Joshua Stein <jsstein@sandia.gov>
Date: Tue, 9 Jun 2020 17:40:46 -0600
Subject: [PATCH 03/27] update what's new documentation

---
 docs/sphinx/source/whatsnew/v0.8.0.rst | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/docs/sphinx/source/whatsnew/v0.8.0.rst b/docs/sphinx/source/whatsnew/v0.8.0.rst
index dc6bf5015c..382f3b91de 100644
--- a/docs/sphinx/source/whatsnew/v0.8.0.rst
+++ b/docs/sphinx/source/whatsnew/v0.8.0.rst
@@ -11,6 +11,7 @@ Enhancements
 
 Bug fixes
 ~~~~~~~~~
+* Fixed unit and default value errors in :py:func:`pvlib.soiling.hsu`. (:pull:`XXX`)
 
 Testing
 ~~~~~~~
@@ -32,3 +33,4 @@ Contributors
 * Cliff Hansen (:ghuser:`cwhanse`)
 * Kevin Anderson (:ghuser:`kanderso-nrel`)
 * Mark Mikofski (:ghuser:`mikofski`)
+* Joshua S. Stein (:ghuser:`jsstein`)

From f412ddb3c56f559de89b63a06cb854e9856845d3 Mon Sep 17 00:00:00 2001
From: Joshua Stein <jsstein@sandia.gov>
Date: Wed, 10 Jun 2020 20:15:43 -0600
Subject: [PATCH 04/27] Fixed stickler-ci issues in test_soiling.py

---
 pvlib/tests/test_soiling.py | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/pvlib/tests/test_soiling.py b/pvlib/tests/test_soiling.py
index eafe11ddf5..e8d8931379 100644
--- a/pvlib/tests/test_soiling.py
+++ b/pvlib/tests/test_soiling.py
@@ -44,12 +44,12 @@ def expected_output_1():
 def expected_output_2():
     dt = pd.date_range(start=pd.Timestamp(2019, 1, 1, 0, 0, 0),
                        end=pd.Timestamp(2019, 1, 1, 23, 59, 0), freq='1h')
-    expected_output_2 = pd.Series(  
-            data = [0.97229869, 0.95035106, 0.93037619, 0.91176175, 1.,
-            1.        , 1.        , 0.97229869, 1.        , 1.        ,
-            1.        , 1.        , 0.97229869, 0.95035106, 0.93037619,
-            0.91176175, 0.89425431, 1.        , 1.        , 1.        ,
-            1.        , 0.97229869, 0.95035106, 0.93037619],
+    expected_output_2 = pd.Series(
+        data=[0.97229869, 0.95035106, 0.93037619, 0.91176175, 1.,
+              1.        , 1.        , 0.97229869, 1.        , 1.        ,
+              1.        , 1.        , 0.97229869, 0.95035106, 0.93037619,
+              0.91176175, 0.89425431, 1.        , 1.        , 1.        ,
+              1.        , 0.97229869, 0.95035106, 0.93037619],
         index=dt)
 
     return expected_output_2
@@ -110,8 +110,8 @@ def test_hsu_defaults(rainfall_input, expected_output_1):
     accumulation period.
     """
     result = hsu(
-        rainfall=rainfall_input, cleaning_threshold=0.5, tilt=0.0, pm2_5=1.0e-2,
-        pm10=2.0e-2)
+        rainfall=rainfall_input, cleaning_threshold=0.5, tilt=0.0, i
+        pm2_5=1.0e-2,pm10=2.0e-2)
     assert np.allclose(result.values, expected_output_1)
 
 

From db6bb166a6961a66839d30bf7a3fb18e744f3546 Mon Sep 17 00:00:00 2001
From: Joshua Stein <jsstein@sandia.gov>
Date: Wed, 10 Jun 2020 20:50:11 -0600
Subject: [PATCH 05/27] Fixed errant character in test

---
 pvlib/tests/test_soiling.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pvlib/tests/test_soiling.py b/pvlib/tests/test_soiling.py
index e8d8931379..ac15053adf 100644
--- a/pvlib/tests/test_soiling.py
+++ b/pvlib/tests/test_soiling.py
@@ -110,7 +110,7 @@ def test_hsu_defaults(rainfall_input, expected_output_1):
     accumulation period.
     """
     result = hsu(
-        rainfall=rainfall_input, cleaning_threshold=0.5, tilt=0.0, i
+        rainfall=rainfall_input, cleaning_threshold=0.5, tilt=0.0,
         pm2_5=1.0e-2,pm10=2.0e-2)
     assert np.allclose(result.values, expected_output_1)
 

From 13bf88f0b8223c7aee54e85bdc90eb377d31b413 Mon Sep 17 00:00:00 2001
From: Joshua Stein <jsstein@sandia.gov>
Date: Fri, 12 Jun 2020 11:31:35 -0600
Subject: [PATCH 06/27] allowed function to accept aribtrary time intervals

---
 pvlib/soiling.py | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/pvlib/soiling.py b/pvlib/soiling.py
index 0bdc6228a5..9ee94e5435 100644
--- a/pvlib/soiling.py
+++ b/pvlib/soiling.py
@@ -12,8 +12,8 @@
 def hsu(rainfall, cleaning_threshold, tilt, pm2_5, pm10,
         depo_veloc=None, rain_accum_period=pd.Timedelta('1h')):
     """
-    Calculates soiling ratio given particulate and rain data using the model
-    from Humboldt State University (HSU).
+    Calculates soiling ratio given particulate and rain data using the 
+    Fixed Velocity model from Humboldt State University (HSU).
 
     The HSU soiling model [1]_ returns the soiling ratio, a value between zero
     and one which is equivalent to (1 - transmission loss). Therefore a soiling
@@ -75,9 +75,16 @@ def hsu(rainfall, cleaning_threshold, tilt, pm2_5, pm10,
     accum_rain = rainfall.rolling(rain_accum_period, closed='right').sum()
     # cleaning is True for intervals with rainfall greater than threshold
     cleaning_times = accum_rain.index[accum_rain >= cleaning_threshold]
+    
+    # determine the time intervals in seconds (dt_sec)
+    dt = rainfall.index.values       # datetimes in nanoseconds
+    dt2 = np.roll(dt.copy(),1)       # shift array values by one place
+    dt3 = np.delete((dt-dt2)/1e9,0)  # subtract shifted values from original and convert to seconds
+    # append the last value to the end so there are the same number of elements in the array
+    dt_sec = np.append(dt3,dt3[-1]).astype('float64') 
 
     horiz_mass_rate = pm2_5 * depo_veloc['2_5']\
-        + np.maximum(pm10 - pm2_5, 0.) * depo_veloc['10'] * 3600
+        + np.maximum(pm10 - pm2_5, 0.) * depo_veloc['10'] * dt_sec
     tilted_mass_rate = horiz_mass_rate * cosd(tilt)  # assuming no rain
 
     # tms -> tilt_mass_rate

From 820b87c79d412931557d9593375de1fa4dc3e803 Mon Sep 17 00:00:00 2001
From: Joshua Stein <jsstein@sandia.gov>
Date: Fri, 12 Jun 2020 13:57:57 -0600
Subject: [PATCH 07/27] updated v0.8.0.rst file

---
 docs/sphinx/source/whatsnew/v0.8.0.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/docs/sphinx/source/whatsnew/v0.8.0.rst b/docs/sphinx/source/whatsnew/v0.8.0.rst
index 382f3b91de..436423c535 100644
--- a/docs/sphinx/source/whatsnew/v0.8.0.rst
+++ b/docs/sphinx/source/whatsnew/v0.8.0.rst
@@ -12,6 +12,7 @@ Enhancements
 Bug fixes
 ~~~~~~~~~
 * Fixed unit and default value errors in :py:func:`pvlib.soiling.hsu`. (:pull:`XXX`)
+* Added ability for :py:func:`pvlib.soiling.hsu` to accept arbitrary time intervals. (:pull:`XXX`)
 
 Testing
 ~~~~~~~

From ffb3c351444e4ba515d0f2a104f46406ddc6f0f5 Mon Sep 17 00:00:00 2001
From: Joshua Stein <jsstein@sandia.gov>
Date: Wed, 17 Jun 2020 15:41:27 -0600
Subject: [PATCH 08/27] Add variable time interval functionality and testing to
 soiling.hsu(), also corrected horiz_mass_rate equation

---
 pvlib/soiling.py            |  4 +--
 pvlib/tests/test_soiling.py | 64 +++++++++++++++++++++++++++----------
 2 files changed, 50 insertions(+), 18 deletions(-)

diff --git a/pvlib/soiling.py b/pvlib/soiling.py
index 9ee94e5435..3dfd41b532 100644
--- a/pvlib/soiling.py
+++ b/pvlib/soiling.py
@@ -83,8 +83,8 @@ def hsu(rainfall, cleaning_threshold, tilt, pm2_5, pm10,
     # append the last value to the end so there are the same number of elements in the array
     dt_sec = np.append(dt3,dt3[-1]).astype('float64') 
 
-    horiz_mass_rate = pm2_5 * depo_veloc['2_5']\
-        + np.maximum(pm10 - pm2_5, 0.) * depo_veloc['10'] * dt_sec
+    horiz_mass_rate = (pm2_5 * depo_veloc['2_5']\
+        + np.maximum(pm10 - pm2_5, 0.) * depo_veloc['10']) * dt_sec
     tilted_mass_rate = horiz_mass_rate * cosd(tilt)  # assuming no rain
 
     # tms -> tilt_mass_rate
diff --git a/pvlib/tests/test_soiling.py b/pvlib/tests/test_soiling.py
index ac15053adf..011699a539 100644
--- a/pvlib/tests/test_soiling.py
+++ b/pvlib/tests/test_soiling.py
@@ -19,11 +19,11 @@ def expected_output():
                        end=pd.Timestamp(2019, 1, 1, 23, 59, 0), freq='1h')
 
     expected_no_cleaning = pd.Series(
-        data=[0.97230454, 0.95036146, 0.93039061, 0.91177978, 0.89427556,
-              0.8777455 , 0.86211038, 0.84731759, 0.83332881, 0.82011354,
-              0.80764549, 0.79590056, 0.78485556, 0.77448749, 0.76477312,
-              0.75568883, 0.74721046, 0.73931338, 0.73197253, 0.72516253,
-              0.7188578 , 0.71303268, 0.7076616 , 0.70271919],
+        data=[0.96998483, 0.94623958, 0.92468139, 0.90465654, 0.88589707,
+              0.86826366, 0.85167258, 0.83606715, 0.82140458, 0.80764919,
+              0.79476875, 0.78273241, 0.77150951, 0.76106905, 0.75137932,
+              0.74240789, 0.73412165, 0.72648695, 0.71946981, 0.7130361 ,
+              0.70715176, 0.70178307, 0.69689677, 0.69246034], 
         index=dt)
     return expected_no_cleaning
 
@@ -32,11 +32,11 @@ def expected_output_1():
     dt = pd.date_range(start=pd.Timestamp(2019, 1, 1, 0, 0, 0),
         end=pd.Timestamp(2019, 1, 1, 23, 59, 0), freq='1h')
     expected_output_1 = pd.Series(
-        data=[0.9872406 , 0.97706269, 0.96769693, 0.95884032, 1.,
-              0.9872406 , 0.97706269, 0.96769693, 1.        , 1.        ,
-              0.9872406 , 0.97706269, 0.96769693, 0.95884032, 0.95036001,
-              0.94218263, 0.93426236, 0.92656836, 0.91907873, 0.91177728,
-              0.9046517 , 0.89769238, 0.89089165, 0.88424329],
+        data=[0.98484972, 0.97277367, 0.96167471, 0.95119603, 1.        ,
+              0.98484972, 0.97277367, 0.96167471, 1.        , 1.        ,
+              0.98484972, 0.97277367, 0.96167471, 0.95119603, 0.94118234,
+              0.93154854, 0.922242  , 0.91322759, 0.90448058, 0.89598283,
+              0.88772062, 0.87968325, 0.8718622 , 0.86425049], 
         index=dt)
     return expected_output_1
 
@@ -45,15 +45,29 @@ def expected_output_2():
     dt = pd.date_range(start=pd.Timestamp(2019, 1, 1, 0, 0, 0),
                        end=pd.Timestamp(2019, 1, 1, 23, 59, 0), freq='1h')
     expected_output_2 = pd.Series(
-        data=[0.97229869, 0.95035106, 0.93037619, 0.91176175, 1.,
-              1.        , 1.        , 0.97229869, 1.        , 1.        ,
-              1.        , 1.        , 0.97229869, 0.95035106, 0.93037619,
-              0.91176175, 0.89425431, 1.        , 1.        , 1.        ,
-              1.        , 0.97229869, 0.95035106, 0.93037619],
+        data = [0.95036261, 0.91178179, 0.87774818, 0.84732079, 1.        ,
+                1.        , 1.        , 0.95036261, 1.        , 1.        ,
+                1.        , 1.        , 0.95036261, 0.91178179, 0.87774818,
+                0.84732079, 0.8201171 , 1.        , 1.        , 1.        ,
+                1.        , 0.95036261, 0.91178179, 0.87774818],
         index=dt)
-
     return expected_output_2
 
+@pytest.fixture
+def expected_output_3():
+    dt = pd.date_range(start=pd.Timestamp(2019, 1, 1, 0, 0, 0),
+                       end=pd.Timestamp(2019, 1, 1, 23, 59, 0), freq='1h')
+    timedelta = [0,0,0,0,0,30,0,30,0,30,0,-30,-30,-30,0,0,0,0,0,0,0,0,0,0]
+    dt_new = dt + pd.to_timedelta(timedelta,'m')
+    expected_output_3 = pd.Series(
+        data = [0.96576705, 0.9387675 , 0.91437615, 0.89186852, 1.        ,
+                1.        , 0.95185738, 0.9387675 , 1.        , 1.        ,
+                1.        , 1.        , 0.96576705, 0.92630786, 0.90291005,
+                0.88122293, 0.86104089, 1.        , 1.        , 1.        ,
+                0.96576705, 0.9387675 , 0.91437615, 0.89186852],
+        index=dt_new)
+    return expected_output_3
+
 @pytest.fixture
 def rainfall_input():
 
@@ -114,6 +128,24 @@ def test_hsu_defaults(rainfall_input, expected_output_1):
         pm2_5=1.0e-2,pm10=2.0e-2)
     assert np.allclose(result.values, expected_output_1)
 
+@requires_scipy
+@needs_pandas_0_22
+def test_hsu_variable_time_intervals(rainfall_input, expected_output_3):
+    """
+    Test Soiling HSU function with variable time intervals.
+    """
+    depo_veloc = {'2_5': 1.0e-4, '10': 1.0e-4}
+    rain = pd.DataFrame(data=rainfall_input)
+    #define time deltas in minutes
+    timedelta = [0,0,0,0,0,30,0,30,0,30,0,-30,-30,-30,0,0,0,0,0,0,0,0,0,0]
+    rain['mins_added'] = pd.to_timedelta(timedelta,'m')
+    rain['new_time'] = rain.index + rain['mins_added']
+    rain_var_times = rain.set_index('new_time').iloc[:,0]
+    result = hsu(
+        rainfall=rain_var_times, cleaning_threshold=0.5, tilt=50.0,
+        pm2_5=1,pm10=2,depo_veloc=depo_veloc,
+        rain_accum_period=pd.Timedelta('2h'))
+    assert np.allclose(result.values, expected_output_3)
 
 @pytest.fixture
 def greensboro_rain():

From 5e5e360bfa809e42bb7fd014a5145d11d4f103c7 Mon Sep 17 00:00:00 2001
From: Joshua Stein <jsstein@sandia.gov>
Date: Wed, 17 Jun 2020 15:48:45 -0600
Subject: [PATCH 09/27] fixed typo in test_soiling.py

---
 pvlib/tests/test_soiling.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pvlib/tests/test_soiling.py b/pvlib/tests/test_soiling.py
index 011699a539..9fe71ff068 100644
--- a/pvlib/tests/test_soiling.py
+++ b/pvlib/tests/test_soiling.py
@@ -145,7 +145,7 @@ def test_hsu_variable_time_intervals(rainfall_input, expected_output_3):
         rainfall=rain_var_times, cleaning_threshold=0.5, tilt=50.0,
         pm2_5=1,pm10=2,depo_veloc=depo_veloc,
         rain_accum_period=pd.Timedelta('2h'))
-    assert np.allclose(result.values, expected_output_3)
+    assert np.allclose(result, expected_output_3)
 
 @pytest.fixture
 def greensboro_rain():

From bc73f512ce35b88e0e083c5fec02904664ce4f93 Mon Sep 17 00:00:00 2001
From: Joshua Stein <jsstein@sandia.gov>
Date: Wed, 17 Jun 2020 16:01:08 -0600
Subject: [PATCH 10/27] fixed stickler-ci errors

---
 pvlib/tests/test_soiling.py | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/pvlib/tests/test_soiling.py b/pvlib/tests/test_soiling.py
index 9fe71ff068..8a29f44cd7 100644
--- a/pvlib/tests/test_soiling.py
+++ b/pvlib/tests/test_soiling.py
@@ -22,8 +22,8 @@ def expected_output():
         data=[0.96998483, 0.94623958, 0.92468139, 0.90465654, 0.88589707,
               0.86826366, 0.85167258, 0.83606715, 0.82140458, 0.80764919,
               0.79476875, 0.78273241, 0.77150951, 0.76106905, 0.75137932,
-              0.74240789, 0.73412165, 0.72648695, 0.71946981, 0.7130361 ,
-              0.70715176, 0.70178307, 0.69689677, 0.69246034], 
+              0.74240789, 0.73412165, 0.72648695, 0.71946981, 0.7130361,
+              0.70715176, 0.70178307, 0.69689677, 0.69246034],
         index=dt)
     return expected_no_cleaning
 
@@ -36,7 +36,7 @@ def expected_output_1():
               0.98484972, 0.97277367, 0.96167471, 1.        , 1.        ,
               0.98484972, 0.97277367, 0.96167471, 0.95119603, 0.94118234,
               0.93154854, 0.922242  , 0.91322759, 0.90448058, 0.89598283,
-              0.88772062, 0.87968325, 0.8718622 , 0.86425049], 
+              0.88772062, 0.87968325, 0.8718622 , 0.86425049],
         index=dt)
     return expected_output_1
 
@@ -53,13 +53,14 @@ def expected_output_2():
         index=dt)
     return expected_output_2
 
+
 @pytest.fixture
 def expected_output_3():
     dt = pd.date_range(start=pd.Timestamp(2019, 1, 1, 0, 0, 0),
                        end=pd.Timestamp(2019, 1, 1, 23, 59, 0), freq='1h')
     timedelta = [0,0,0,0,0,30,0,30,0,30,0,-30,-30,-30,0,0,0,0,0,0,0,0,0,0]
     dt_new = dt + pd.to_timedelta(timedelta,'m')
-    expected_output_3 = pd.Series(
+    expected_output_3=pd.Series(
         data = [0.96576705, 0.9387675 , 0.91437615, 0.89186852, 1.        ,
                 1.        , 0.95185738, 0.9387675 , 1.        , 1.        ,
                 1.        , 1.        , 0.96576705, 0.92630786, 0.90291005,

From 617e445683f7b7c9ae38086d0c1ca89356998d8a Mon Sep 17 00:00:00 2001
From: Joshua Stein <jsstein@sandia.gov>
Date: Wed, 17 Jun 2020 16:02:42 -0600
Subject: [PATCH 11/27] fixed more formatting errors

---
 pvlib/soiling.py | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/pvlib/soiling.py b/pvlib/soiling.py
index 3dfd41b532..551924746c 100644
--- a/pvlib/soiling.py
+++ b/pvlib/soiling.py
@@ -12,7 +12,7 @@
 def hsu(rainfall, cleaning_threshold, tilt, pm2_5, pm10,
         depo_veloc=None, rain_accum_period=pd.Timedelta('1h')):
     """
-    Calculates soiling ratio given particulate and rain data using the 
+    Calculates soiling ratio given particulate and rain data using the
     Fixed Velocity model from Humboldt State University (HSU).
 
     The HSU soiling model [1]_ returns the soiling ratio, a value between zero
@@ -75,13 +75,14 @@ def hsu(rainfall, cleaning_threshold, tilt, pm2_5, pm10,
     accum_rain = rainfall.rolling(rain_accum_period, closed='right').sum()
     # cleaning is True for intervals with rainfall greater than threshold
     cleaning_times = accum_rain.index[accum_rain >= cleaning_threshold]
-    
+
     # determine the time intervals in seconds (dt_sec)
     dt = rainfall.index.values       # datetimes in nanoseconds
-    dt2 = np.roll(dt.copy(),1)       # shift array values by one place
-    dt3 = np.delete((dt-dt2)/1e9,0)  # subtract shifted values from original and convert to seconds
-    # append the last value to the end so there are the same number of elements in the array
-    dt_sec = np.append(dt3,dt3[-1]).astype('float64') 
+    dt2 = np.roll(dt.copy(), 1)       # shift array values by one place
+    # subtract shifted values from original and convert to seconds
+    dt3 = np.delete((dt-dt2)/1e9, 0)
+    # append last value to end so same number of elements in the array
+    dt_sec = np.append(dt3, dt3[-1]).astype('float64') 
 
     horiz_mass_rate = (pm2_5 * depo_veloc['2_5']\
         + np.maximum(pm10 - pm2_5, 0.) * depo_veloc['10']) * dt_sec

From 875f298d4630ab9ea04e22cdf417d3cc3dc27ee5 Mon Sep 17 00:00:00 2001
From: Joshua Stein <jsstein@sandia.gov>
Date: Wed, 17 Jun 2020 16:09:46 -0600
Subject: [PATCH 12/27] more stickler-ci issues fixed

---
 pvlib/soiling.py            |  4 ++--
 pvlib/tests/test_soiling.py | 15 ++++++++-------
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/pvlib/soiling.py b/pvlib/soiling.py
index 551924746c..5053f4883b 100644
--- a/pvlib/soiling.py
+++ b/pvlib/soiling.py
@@ -82,9 +82,9 @@ def hsu(rainfall, cleaning_threshold, tilt, pm2_5, pm10,
     # subtract shifted values from original and convert to seconds
     dt3 = np.delete((dt-dt2)/1e9, 0)
     # append last value to end so same number of elements in the array
-    dt_sec = np.append(dt3, dt3[-1]).astype('float64') 
+    dt_sec = np.append(dt3, dt3[-1]).astype('float64')
 
-    horiz_mass_rate = (pm2_5 * depo_veloc['2_5']\
+    horiz_mass_rate = (pm2_5 * depo_veloc['2_5']
         + np.maximum(pm10 - pm2_5, 0.) * depo_veloc['10']) * dt_sec
     tilted_mass_rate = horiz_mass_rate * cosd(tilt)  # assuming no rain
 
diff --git a/pvlib/tests/test_soiling.py b/pvlib/tests/test_soiling.py
index 8a29f44cd7..1f68ecd9a4 100644
--- a/pvlib/tests/test_soiling.py
+++ b/pvlib/tests/test_soiling.py
@@ -60,12 +60,12 @@ def expected_output_3():
                        end=pd.Timestamp(2019, 1, 1, 23, 59, 0), freq='1h')
     timedelta = [0,0,0,0,0,30,0,30,0,30,0,-30,-30,-30,0,0,0,0,0,0,0,0,0,0]
     dt_new = dt + pd.to_timedelta(timedelta,'m')
-    expected_output_3=pd.Series(
-        data = [0.96576705, 0.9387675 , 0.91437615, 0.89186852, 1.        ,
-                1.        , 0.95185738, 0.9387675 , 1.        , 1.        ,
-                1.        , 1.        , 0.96576705, 0.92630786, 0.90291005,
-                0.88122293, 0.86104089, 1.        , 1.        , 1.        ,
-                0.96576705, 0.9387675 , 0.91437615, 0.89186852],
+    expected_output_3 = pd.Series(
+        data=[0.96576705, 0.9387675 , 0.91437615, 0.89186852, 1.        ,
+              1.        , 0.95185738, 0.9387675 , 1.        , 1.        ,
+              1.        , 1.        , 0.96576705, 0.92630786, 0.90291005,
+              0.88122293, 0.86104089, 1.        , 1.        , 1.        ,
+              0.96576705, 0.9387675 , 0.91437615, 0.89186852],
         index=dt_new)
     return expected_output_3
 
@@ -129,6 +129,7 @@ def test_hsu_defaults(rainfall_input, expected_output_1):
         pm2_5=1.0e-2,pm10=2.0e-2)
     assert np.allclose(result.values, expected_output_1)
 
+
 @requires_scipy
 @needs_pandas_0_22
 def test_hsu_variable_time_intervals(rainfall_input, expected_output_3):
@@ -137,7 +138,7 @@ def test_hsu_variable_time_intervals(rainfall_input, expected_output_3):
     """
     depo_veloc = {'2_5': 1.0e-4, '10': 1.0e-4}
     rain = pd.DataFrame(data=rainfall_input)
-    #define time deltas in minutes
+    # define time deltas in minutes
     timedelta = [0,0,0,0,0,30,0,30,0,30,0,-30,-30,-30,0,0,0,0,0,0,0,0,0,0]
     rain['mins_added'] = pd.to_timedelta(timedelta,'m')
     rain['new_time'] = rain.index + rain['mins_added']

From 254bffa7cb095592cc48cc67f3f4aabad0f65e92 Mon Sep 17 00:00:00 2001
From: Joshua Stein <jsstein@sandia.gov>
Date: Thu, 18 Jun 2020 11:26:54 -0600
Subject: [PATCH 13/27] fixed more stickler-ci issues

---
 pvlib/soiling.py            |  5 +++--
 pvlib/tests/test_soiling.py | 41 +++++++++++++++++++------------------
 2 files changed, 24 insertions(+), 22 deletions(-)

diff --git a/pvlib/soiling.py b/pvlib/soiling.py
index c5b9f0f759..7eead793a5 100644
--- a/pvlib/soiling.py
+++ b/pvlib/soiling.py
@@ -84,8 +84,9 @@ def hsu(rainfall, cleaning_threshold, tilt, pm2_5, pm10,
     # append last value to end so same number of elements in the array
     dt_sec = np.append(dt3, dt3[-1]).astype('float64')
 
-    horiz_mass_rate = (pm2_5 * depo_veloc['2_5']\
-        + np.maximum(pm10 - pm2_5, 0.) * depo_veloc['10']) * dt_sec
+    horiz_mass_rate = (
+        pm2_5 * depo_veloc['2_5'] + np.maximum(pm10 - pm2_5, 0.)
+        * depo_veloc['10']) * dt_sec
     tilted_mass_rate = horiz_mass_rate * cosd(tilt)  # assuming no rain
 
     # tms -> tilt_mass_rate
diff --git a/pvlib/tests/test_soiling.py b/pvlib/tests/test_soiling.py
index 445f41fc69..7d453b3c08 100644
--- a/pvlib/tests/test_soiling.py
+++ b/pvlib/tests/test_soiling.py
@@ -32,11 +32,11 @@ def expected_output_1():
     dt = pd.date_range(start=pd.Timestamp(2019, 1, 1, 0, 0, 0),
         end=pd.Timestamp(2019, 1, 1, 23, 59, 0), freq='1h')
     expected_output_1 = pd.Series(
-        data=[0.98484972, 0.97277367, 0.96167471, 0.95119603, 1.        ,
-              0.98484972, 0.97277367, 0.96167471, 1.        , 1.        ,
+        data=[0.98484972, 0.97277367, 0.96167471, 0.95119603, 1.        ,  #noqa: E203
+              0.98484972, 0.97277367, 0.96167471, 1.        , 1.        ,  #noqa: E203
               0.98484972, 0.97277367, 0.96167471, 0.95119603, 0.94118234,
-              0.93154854, 0.922242  , 0.91322759, 0.90448058, 0.89598283,
-              0.88772062, 0.87968325, 0.8718622 , 0.86425049],
+              0.93154854, 0.922242  , 0.91322759, 0.90448058, 0.89598283,  #noqa: E203
+              0.88772062, 0.87968325, 0.8718622 , 0.86425049],  #noqa: E203
         index=dt)
     return expected_output_1
 
@@ -45,26 +45,27 @@ def expected_output_2():
     dt = pd.date_range(start=pd.Timestamp(2019, 1, 1, 0, 0, 0),
                        end=pd.Timestamp(2019, 1, 1, 23, 59, 0), freq='1h')
     expected_output_2 = pd.Series(
-        data = [0.95036261, 0.91178179, 0.87774818, 0.84732079, 1.        ,
-                1.        , 1.        , 0.95036261, 1.        , 1.        ,
-                1.        , 1.        , 0.95036261, 0.91178179, 0.87774818,
-                0.84732079, 0.8201171 , 1.        , 1.        , 1.        ,
-                1.        , 0.95036261, 0.91178179, 0.87774818],
+        data=[0.95036261, 0.91178179, 0.87774818, 0.84732079, 1.        ,  #noqa: E203
+              1.        , 1.        , 0.95036261, 1.        , 1.        ,  #noqa: E203
+              1.        , 1.        , 0.95036261, 0.91178179, 0.87774818,  #noqa: E203
+              0.84732079, 0.8201171 , 1.        , 1.        , 1.        ,  #noqa: E203
+              1.        , 0.95036261, 0.91178179, 0.87774818],  #noqa: E203
         index=dt)
     return expected_output_2
 
+
 @pytest.fixture
 def expected_output_3():
     dt = pd.date_range(start=pd.Timestamp(2019, 1, 1, 0, 0, 0),
                        end=pd.Timestamp(2019, 1, 1, 23, 59, 0), freq='1h')
-    timedelta = [0,0,0,0,0,30,0,30,0,30,0,-30,-30,-30,0,0,0,0,0,0,0,0,0,0]
-    dt_new = dt + pd.to_timedelta(timedelta,'m')
+    timedelta = [0, 0, 0, 0, 0, 30, 0, 30, 0, 30, 0, -30, -30, -30, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
+    dt_new = dt + pd.to_timedelta(timedelta, 'm')
     expected_output_3 = pd.Series(
-        data=[0.96576705, 0.9387675 , 0.91437615, 0.89186852, 1.        ,
-              1.        , 0.95185738, 0.9387675 , 1.        , 1.        ,
-              1.        , 1.        , 0.96576705, 0.92630786, 0.90291005,
-              0.88122293, 0.86104089, 1.        , 1.        , 1.        ,
-              0.96576705, 0.9387675 , 0.91437615, 0.89186852],
+        data=[0.96576705, 0.9387675 , 0.91437615, 0.89186852, 1.        ,  #noqa: E203
+              1.        , 0.95185738, 0.9387675 , 1.        , 1.        ,  #noqa: E203
+              1.        , 1.        , 0.96576705, 0.92630786, 0.90291005,  #noqa: E203
+              0.88122293, 0.86104089, 1.        , 1.        , 1.        ,  #noqa: E203
+              0.96576705, 0.9387675 , 0.91437615, 0.89186852],  #noqa: E203
         index=dt_new)
     return expected_output_3
 
@@ -138,13 +139,13 @@ def test_hsu_variable_time_intervals(rainfall_input, expected_output_3):
     depo_veloc = {'2_5': 1.0e-4, '10': 1.0e-4}
     rain = pd.DataFrame(data=rainfall_input)
     # define time deltas in minutes
-    timedelta = [0,0,0,0,0,30,0,30,0,30,0,-30,-30,-30,0,0,0,0,0,0,0,0,0,0]
-    rain['mins_added'] = pd.to_timedelta(timedelta,'m')
+    timedelta = [0, 0, 0, 0, 0, 30, 0, 30, 0, 30, 0, -30, -30, -30, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
+    rain['mins_added'] = pd.to_timedelta(timedelta, 'm')
     rain['new_time'] = rain.index + rain['mins_added']
-    rain_var_times = rain.set_index('new_time').iloc[:,0]
+    rain_var_times = rain.set_index('new_time').iloc[:, 0]
     result = hsu(
         rainfall=rain_var_times, cleaning_threshold=0.5, tilt=50.0,
-        pm2_5=1,pm10=2,depo_veloc=depo_veloc,
+        pm2_5=1, pm10=2, depo_veloc=depo_veloc,
         rain_accum_period=pd.Timedelta('2h'))
     assert np.allclose(result, expected_output_3)
 

From 5f83509941d0ce28f93c40ca0d392626e33e7ec0 Mon Sep 17 00:00:00 2001
From: Joshua Stein <jsstein@sandia.gov>
Date: Thu, 18 Jun 2020 11:40:57 -0600
Subject: [PATCH 14/27] formatting issues

---
 pvlib/soiling.py            |  2 +-
 pvlib/tests/test_soiling.py | 32 ++++++++++++++++----------------
 2 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/pvlib/soiling.py b/pvlib/soiling.py
index 7eead793a5..97303435c3 100644
--- a/pvlib/soiling.py
+++ b/pvlib/soiling.py
@@ -86,7 +86,7 @@ def hsu(rainfall, cleaning_threshold, tilt, pm2_5, pm10,
 
     horiz_mass_rate = (
         pm2_5 * depo_veloc['2_5'] + np.maximum(pm10 - pm2_5, 0.)
-        * depo_veloc['10']) * dt_sec
+        * depo_veloc['10']) * dt_sec  # noqa: W503
     tilted_mass_rate = horiz_mass_rate * cosd(tilt)  # assuming no rain
 
     # tms -> tilt_mass_rate
diff --git a/pvlib/tests/test_soiling.py b/pvlib/tests/test_soiling.py
index 7d453b3c08..b56fdbee3e 100644
--- a/pvlib/tests/test_soiling.py
+++ b/pvlib/tests/test_soiling.py
@@ -32,11 +32,11 @@ def expected_output_1():
     dt = pd.date_range(start=pd.Timestamp(2019, 1, 1, 0, 0, 0),
         end=pd.Timestamp(2019, 1, 1, 23, 59, 0), freq='1h')
     expected_output_1 = pd.Series(
-        data=[0.98484972, 0.97277367, 0.96167471, 0.95119603, 1.        ,  #noqa: E203
-              0.98484972, 0.97277367, 0.96167471, 1.        , 1.        ,  #noqa: E203
+        data=[0.98484972, 0.97277367, 0.96167471, 0.95119603, 1.,
+              0.98484972, 0.97277367, 0.96167471, 1.        , 1.,
               0.98484972, 0.97277367, 0.96167471, 0.95119603, 0.94118234,
-              0.93154854, 0.922242  , 0.91322759, 0.90448058, 0.89598283,  #noqa: E203
-              0.88772062, 0.87968325, 0.8718622 , 0.86425049],  #noqa: E203
+              0.93154854, 0.922242, 0.91322759, 0.90448058, 0.89598283,
+              0.88772062, 0.87968325, 0.8718622, 0.86425049],
         index=dt)
     return expected_output_1
 
@@ -45,11 +45,11 @@ def expected_output_2():
     dt = pd.date_range(start=pd.Timestamp(2019, 1, 1, 0, 0, 0),
                        end=pd.Timestamp(2019, 1, 1, 23, 59, 0), freq='1h')
     expected_output_2 = pd.Series(
-        data=[0.95036261, 0.91178179, 0.87774818, 0.84732079, 1.        ,  #noqa: E203
-              1.        , 1.        , 0.95036261, 1.        , 1.        ,  #noqa: E203
-              1.        , 1.        , 0.95036261, 0.91178179, 0.87774818,  #noqa: E203
-              0.84732079, 0.8201171 , 1.        , 1.        , 1.        ,  #noqa: E203
-              1.        , 0.95036261, 0.91178179, 0.87774818],  #noqa: E203
+        data=[0.95036261, 0.91178179, 0.87774818, 0.84732079, 1.,
+              1., 1., 0.95036261, 1., 1.,
+              1., 1., 0.95036261, 0.91178179, 0.87774818,
+              0.84732079, 0.8201171, 1., 1., 1.,
+              1., 0.95036261, 0.91178179, 0.87774818],
         index=dt)
     return expected_output_2
 
@@ -58,14 +58,14 @@ def expected_output_2():
 def expected_output_3():
     dt = pd.date_range(start=pd.Timestamp(2019, 1, 1, 0, 0, 0),
                        end=pd.Timestamp(2019, 1, 1, 23, 59, 0), freq='1h')
-    timedelta = [0, 0, 0, 0, 0, 30, 0, 30, 0, 30, 0, -30, -30, -30, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
+    timedelta = [0,0,0,0,0,30,0,30,0,30,0,-30,-30,-30,0,0,0,0,0,0,0,0,0,0]
     dt_new = dt + pd.to_timedelta(timedelta, 'm')
     expected_output_3 = pd.Series(
-        data=[0.96576705, 0.9387675 , 0.91437615, 0.89186852, 1.        ,  #noqa: E203
-              1.        , 0.95185738, 0.9387675 , 1.        , 1.        ,  #noqa: E203
-              1.        , 1.        , 0.96576705, 0.92630786, 0.90291005,  #noqa: E203
-              0.88122293, 0.86104089, 1.        , 1.        , 1.        ,  #noqa: E203
-              0.96576705, 0.9387675 , 0.91437615, 0.89186852],  #noqa: E203
+        data=[0.96576705, 0.9387675, 0.91437615, 0.89186852, 1.,
+              1., 0.95185738, 0.9387675, 1., 1.,
+              1., 1., 0.96576705, 0.92630786, 0.90291005,
+              0.88122293, 0.86104089, 1., 1., 1.,
+              0.96576705, 0.9387675, 0.91437615, 0.89186852],
         index=dt_new)
     return expected_output_3
 
@@ -139,7 +139,7 @@ def test_hsu_variable_time_intervals(rainfall_input, expected_output_3):
     depo_veloc = {'2_5': 1.0e-4, '10': 1.0e-4}
     rain = pd.DataFrame(data=rainfall_input)
     # define time deltas in minutes
-    timedelta = [0, 0, 0, 0, 0, 30, 0, 30, 0, 30, 0, -30, -30, -30, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
+    timedelta = [0,0,0,0,0,30,0,30,0,30,0,-30,-30,-30,0,0,0,0,0,0,0,0,0,0]
     rain['mins_added'] = pd.to_timedelta(timedelta, 'm')
     rain['new_time'] = rain.index + rain['mins_added']
     rain_var_times = rain.set_index('new_time').iloc[:, 0]

From d25d6b2908d6fed5b631729e13daf929ae4f4484 Mon Sep 17 00:00:00 2001
From: Joshua Stein <jsstein@sandia.gov>
Date: Thu, 18 Jun 2020 11:46:15 -0600
Subject: [PATCH 15/27] formatting issues

---
 pvlib/tests/test_soiling.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/pvlib/tests/test_soiling.py b/pvlib/tests/test_soiling.py
index b56fdbee3e..c6e15ae74d 100644
--- a/pvlib/tests/test_soiling.py
+++ b/pvlib/tests/test_soiling.py
@@ -33,7 +33,7 @@ def expected_output_1():
         end=pd.Timestamp(2019, 1, 1, 23, 59, 0), freq='1h')
     expected_output_1 = pd.Series(
         data=[0.98484972, 0.97277367, 0.96167471, 0.95119603, 1.,
-              0.98484972, 0.97277367, 0.96167471, 1.        , 1.,
+              0.98484972, 0.97277367, 0.96167471, 1., 1.,
               0.98484972, 0.97277367, 0.96167471, 0.95119603, 0.94118234,
               0.93154854, 0.922242, 0.91322759, 0.90448058, 0.89598283,
               0.88772062, 0.87968325, 0.8718622, 0.86425049],
@@ -58,7 +58,7 @@ def expected_output_2():
 def expected_output_3():
     dt = pd.date_range(start=pd.Timestamp(2019, 1, 1, 0, 0, 0),
                        end=pd.Timestamp(2019, 1, 1, 23, 59, 0), freq='1h')
-    timedelta = [0,0,0,0,0,30,0,30,0,30,0,-30,-30,-30,0,0,0,0,0,0,0,0,0,0]
+    timedelta = [0,0,0,0,0,30,0,30,0,30,0,-30,-30,-30,0,0,0,0,0,0,0,0,0,0]  # noqa: E231
     dt_new = dt + pd.to_timedelta(timedelta, 'm')
     expected_output_3 = pd.Series(
         data=[0.96576705, 0.9387675, 0.91437615, 0.89186852, 1.,
@@ -139,7 +139,7 @@ def test_hsu_variable_time_intervals(rainfall_input, expected_output_3):
     depo_veloc = {'2_5': 1.0e-4, '10': 1.0e-4}
     rain = pd.DataFrame(data=rainfall_input)
     # define time deltas in minutes
-    timedelta = [0,0,0,0,0,30,0,30,0,30,0,-30,-30,-30,0,0,0,0,0,0,0,0,0,0]
+    timedelta = [0,0,0,0,0,30,0,30,0,30,0,-30,-30,-30,0,0,0,0,0,0,0,0,0,0]  # noqa: E231
     rain['mins_added'] = pd.to_timedelta(timedelta, 'm')
     rain['new_time'] = rain.index + rain['mins_added']
     rain_var_times = rain.set_index('new_time').iloc[:, 0]

From 551ab85528ef1e4382e8765f5c62787b05089b46 Mon Sep 17 00:00:00 2001
From: Joshua Stein <jsstein@sandia.gov>
Date: Thu, 18 Jun 2020 11:49:52 -0600
Subject: [PATCH 16/27] formatting...

---
 pvlib/tests/test_soiling.py | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/pvlib/tests/test_soiling.py b/pvlib/tests/test_soiling.py
index c6e15ae74d..3fb29dd11b 100644
--- a/pvlib/tests/test_soiling.py
+++ b/pvlib/tests/test_soiling.py
@@ -58,7 +58,8 @@ def expected_output_2():
 def expected_output_3():
     dt = pd.date_range(start=pd.Timestamp(2019, 1, 1, 0, 0, 0),
                        end=pd.Timestamp(2019, 1, 1, 23, 59, 0), freq='1h')
-    timedelta = [0,0,0,0,0,30,0,30,0,30,0,-30,-30,-30,0,0,0,0,0,0,0,0,0,0]  # noqa: E231
+    timedelta = [0, 0, 0, 0, 0, 30, 0, 30, 0, 30, 0, -30,
+        -30, -30, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
     dt_new = dt + pd.to_timedelta(timedelta, 'm')
     expected_output_3 = pd.Series(
         data=[0.96576705, 0.9387675, 0.91437615, 0.89186852, 1.,
@@ -139,7 +140,8 @@ def test_hsu_variable_time_intervals(rainfall_input, expected_output_3):
     depo_veloc = {'2_5': 1.0e-4, '10': 1.0e-4}
     rain = pd.DataFrame(data=rainfall_input)
     # define time deltas in minutes
-    timedelta = [0,0,0,0,0,30,0,30,0,30,0,-30,-30,-30,0,0,0,0,0,0,0,0,0,0]  # noqa: E231
+    timedelta = [0, 0, 0, 0, 0, 30, 0, 30, 0, 30, 0, -30,
+        -30, -30, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
     rain['mins_added'] = pd.to_timedelta(timedelta, 'm')
     rain['new_time'] = rain.index + rain['mins_added']
     rain_var_times = rain.set_index('new_time').iloc[:, 0]

From 400a992459c4169f1918f016b32d3243498b74b7 Mon Sep 17 00:00:00 2001
From: Joshua Stein <jsstein@sandia.gov>
Date: Thu, 18 Jun 2020 11:52:12 -0600
Subject: [PATCH 17/27] formatting.....

---
 pvlib/tests/test_soiling.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pvlib/tests/test_soiling.py b/pvlib/tests/test_soiling.py
index 3fb29dd11b..9aad4ff8ea 100644
--- a/pvlib/tests/test_soiling.py
+++ b/pvlib/tests/test_soiling.py
@@ -59,7 +59,7 @@ def expected_output_3():
     dt = pd.date_range(start=pd.Timestamp(2019, 1, 1, 0, 0, 0),
                        end=pd.Timestamp(2019, 1, 1, 23, 59, 0), freq='1h')
     timedelta = [0, 0, 0, 0, 0, 30, 0, 30, 0, 30, 0, -30,
-        -30, -30, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
+                 -30, -30, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
     dt_new = dt + pd.to_timedelta(timedelta, 'm')
     expected_output_3 = pd.Series(
         data=[0.96576705, 0.9387675, 0.91437615, 0.89186852, 1.,
@@ -141,7 +141,7 @@ def test_hsu_variable_time_intervals(rainfall_input, expected_output_3):
     rain = pd.DataFrame(data=rainfall_input)
     # define time deltas in minutes
     timedelta = [0, 0, 0, 0, 0, 30, 0, 30, 0, 30, 0, -30,
-        -30, -30, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
+                 -30, -30, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
     rain['mins_added'] = pd.to_timedelta(timedelta, 'm')
     rain['new_time'] = rain.index + rain['mins_added']
     rain_var_times = rain.set_index('new_time').iloc[:, 0]

From f88827611bc13183d25775fe271bb2c88baa1789 Mon Sep 17 00:00:00 2001
From: Joshua Stein <jsstein@sandia.gov>
Date: Fri, 19 Jun 2020 16:51:09 -0600
Subject: [PATCH 18/27] changed variable time interval calculation in hsu model
 and test

---
 pvlib/soiling.py            | 8 ++++----
 pvlib/tests/test_soiling.py | 8 ++++----
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/pvlib/soiling.py b/pvlib/soiling.py
index 97303435c3..12077e5394 100644
--- a/pvlib/soiling.py
+++ b/pvlib/soiling.py
@@ -77,12 +77,12 @@ def hsu(rainfall, cleaning_threshold, tilt, pm2_5, pm10,
     cleaning_times = accum_rain.index[accum_rain >= cleaning_threshold]
 
     # determine the time intervals in seconds (dt_sec)
-    dt = rainfall.index.values       # datetimes in nanoseconds
-    dt2 = np.roll(dt.copy(), 1)       # shift array values by one place
+    dt = rainfall.index
+    dt2 = np.roll(dt.copy(),1)
     # subtract shifted values from original and convert to seconds
-    dt3 = np.delete((dt-dt2)/1e9, 0)
+    dt3 = np.delete((dt-dt2),0).total_seconds()
     # append last value to end so same number of elements in the array
-    dt_sec = np.append(dt3, dt3[-1]).astype('float64')
+    dt_sec = np.append(dt3[0], dt3).astype('float64')
 
     horiz_mass_rate = (
         pm2_5 * depo_veloc['2_5'] + np.maximum(pm10 - pm2_5, 0.)
diff --git a/pvlib/tests/test_soiling.py b/pvlib/tests/test_soiling.py
index 9aad4ff8ea..05b3595106 100644
--- a/pvlib/tests/test_soiling.py
+++ b/pvlib/tests/test_soiling.py
@@ -63,10 +63,10 @@ def expected_output_3():
     dt_new = dt + pd.to_timedelta(timedelta, 'm')
     expected_output_3 = pd.Series(
         data=[0.96576705, 0.9387675, 0.91437615, 0.89186852, 1.,
-              1., 0.95185738, 0.9387675, 1., 1.,
-              1., 1., 0.96576705, 0.92630786, 0.90291005,
-              0.88122293, 0.86104089, 1., 1., 1.,
-              0.96576705, 0.9387675, 0.91437615, 0.89186852],
+                1., 0.98093819, 0.9387675, 1., 1.,
+                1., 1., 0.96576705, 0.9387675 , 0.90291005,
+                0.88122293, 0.86104089, 1., 1., 1.,
+                0.96576705, 0.9387675, 0.91437615, 0.89186852],
         index=dt_new)
     return expected_output_3
 

From 066221566fee5ad49e756ab2bdc29c685fdac677 Mon Sep 17 00:00:00 2001
From: Joshua Stein <jsstein@sandia.gov>
Date: Fri, 19 Jun 2020 16:55:47 -0600
Subject: [PATCH 19/27] formatting changes

---
 pvlib/soiling.py            | 4 ++--
 pvlib/tests/test_soiling.py | 8 ++++----
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/pvlib/soiling.py b/pvlib/soiling.py
index 12077e5394..20ceb91215 100644
--- a/pvlib/soiling.py
+++ b/pvlib/soiling.py
@@ -78,9 +78,9 @@ def hsu(rainfall, cleaning_threshold, tilt, pm2_5, pm10,
 
     # determine the time intervals in seconds (dt_sec)
     dt = rainfall.index
-    dt2 = np.roll(dt.copy(),1)
+    dt2 = np.roll(dt.copy(), 1)
     # subtract shifted values from original and convert to seconds
-    dt3 = np.delete((dt-dt2),0).total_seconds()
+    dt3 = np.delete((dt-dt2), 0).total_seconds()
     # append last value to end so same number of elements in the array
     dt_sec = np.append(dt3[0], dt3).astype('float64')
 
diff --git a/pvlib/tests/test_soiling.py b/pvlib/tests/test_soiling.py
index 05b3595106..7261745fd4 100644
--- a/pvlib/tests/test_soiling.py
+++ b/pvlib/tests/test_soiling.py
@@ -63,10 +63,10 @@ def expected_output_3():
     dt_new = dt + pd.to_timedelta(timedelta, 'm')
     expected_output_3 = pd.Series(
         data=[0.96576705, 0.9387675, 0.91437615, 0.89186852, 1.,
-                1., 0.98093819, 0.9387675, 1., 1.,
-                1., 1., 0.96576705, 0.9387675 , 0.90291005,
-                0.88122293, 0.86104089, 1., 1., 1.,
-                0.96576705, 0.9387675, 0.91437615, 0.89186852],
+            1., 0.98093819, 0.9387675, 1., 1.,
+            1., 1., 0.96576705, 0.9387675 , 0.90291005,
+            0.88122293, 0.86104089, 1., 1., 1.,
+            0.96576705, 0.9387675, 0.91437615, 0.89186852],
         index=dt_new)
     return expected_output_3
 

From 6cd354e4aa7fa046352768bb63193847d61b4bd8 Mon Sep 17 00:00:00 2001
From: Joshua Stein <jsstein@sandia.gov>
Date: Fri, 19 Jun 2020 16:58:07 -0600
Subject: [PATCH 20/27] formatting

---
 pvlib/tests/test_soiling.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/pvlib/tests/test_soiling.py b/pvlib/tests/test_soiling.py
index 7261745fd4..56bc731ca0 100644
--- a/pvlib/tests/test_soiling.py
+++ b/pvlib/tests/test_soiling.py
@@ -63,10 +63,10 @@ def expected_output_3():
     dt_new = dt + pd.to_timedelta(timedelta, 'm')
     expected_output_3 = pd.Series(
         data=[0.96576705, 0.9387675, 0.91437615, 0.89186852, 1.,
-            1., 0.98093819, 0.9387675, 1., 1.,
-            1., 1., 0.96576705, 0.9387675 , 0.90291005,
-            0.88122293, 0.86104089, 1., 1., 1.,
-            0.96576705, 0.9387675, 0.91437615, 0.89186852],
+             1., 0.98093819, 0.9387675, 1., 1.,
+             1., 1., 0.96576705, 0.9387675, 0.90291005,
+             0.88122293, 0.86104089, 1., 1., 1.,
+             0.96576705, 0.9387675, 0.91437615, 0.89186852],
         index=dt_new)
     return expected_output_3
 

From 9122281e94d7ac69020f0ca8f7e86cfad510adeb Mon Sep 17 00:00:00 2001
From: Joshua Stein <jsstein@sandia.gov>
Date: Fri, 19 Jun 2020 17:03:08 -0600
Subject: [PATCH 21/27] formatting

---
 pvlib/tests/test_soiling.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/pvlib/tests/test_soiling.py b/pvlib/tests/test_soiling.py
index 56bc731ca0..01cd506921 100644
--- a/pvlib/tests/test_soiling.py
+++ b/pvlib/tests/test_soiling.py
@@ -63,10 +63,10 @@ def expected_output_3():
     dt_new = dt + pd.to_timedelta(timedelta, 'm')
     expected_output_3 = pd.Series(
         data=[0.96576705, 0.9387675, 0.91437615, 0.89186852, 1.,
-             1., 0.98093819, 0.9387675, 1., 1.,
-             1., 1., 0.96576705, 0.9387675, 0.90291005,
-             0.88122293, 0.86104089, 1., 1., 1.,
-             0.96576705, 0.9387675, 0.91437615, 0.89186852],
+              1., 0.98093819, 0.9387675, 1., 1., 
+              1., 1., 0.96576705, 0.9387675, 0.90291005, 
+              0.88122293, 0.86104089, 1., 1., 1., 
+              0.96576705, 0.9387675, 0.91437615, 0.89186852], 
         index=dt_new)
     return expected_output_3
 

From b864eb9739b6d5ff9d9c32745f8acf3542921381 Mon Sep 17 00:00:00 2001
From: Joshua Stein <jsstein@sandia.gov>
Date: Fri, 19 Jun 2020 17:04:51 -0600
Subject: [PATCH 22/27] formatting

---
 pvlib/tests/test_soiling.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/pvlib/tests/test_soiling.py b/pvlib/tests/test_soiling.py
index 01cd506921..76c8fcfe2d 100644
--- a/pvlib/tests/test_soiling.py
+++ b/pvlib/tests/test_soiling.py
@@ -63,10 +63,10 @@ def expected_output_3():
     dt_new = dt + pd.to_timedelta(timedelta, 'm')
     expected_output_3 = pd.Series(
         data=[0.96576705, 0.9387675, 0.91437615, 0.89186852, 1.,
-              1., 0.98093819, 0.9387675, 1., 1., 
-              1., 1., 0.96576705, 0.9387675, 0.90291005, 
-              0.88122293, 0.86104089, 1., 1., 1., 
-              0.96576705, 0.9387675, 0.91437615, 0.89186852], 
+              1., 0.98093819, 0.9387675, 1., 1.,
+              1., 1., 0.96576705, 0.9387675, 0.90291005,
+              0.88122293, 0.86104089, 1., 1., 1.,
+              0.96576705, 0.9387675, 0.91437615, 0.89186852],
         index=dt_new)
     return expected_output_3
 

From 020b7d2d6a2418af8c0fef06529df4fcbf559a62 Mon Sep 17 00:00:00 2001
From: Kevin Anderson <kevin.anderson@nrel.gov>
Date: Wed, 26 Aug 2020 18:39:05 -0600
Subject: [PATCH 23/27] whatsnew PR links

---
 docs/sphinx/source/whatsnew/v0.8.0.rst | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/docs/sphinx/source/whatsnew/v0.8.0.rst b/docs/sphinx/source/whatsnew/v0.8.0.rst
index beca0526c5..94b81e1f38 100644
--- a/docs/sphinx/source/whatsnew/v0.8.0.rst
+++ b/docs/sphinx/source/whatsnew/v0.8.0.rst
@@ -14,8 +14,8 @@ Enhancements
 
 Bug fixes
 ~~~~~~~~~
-* Fixed unit and default value errors in :py:func:`pvlib.soiling.hsu`. (:pull:`XXX`)
-* Added ability for :py:func:`pvlib.soiling.hsu` to accept arbitrary time intervals. (:pull:`XXX`)
+* Fixed unit and default value errors in :py:func:`pvlib.soiling.hsu`. (:pull:`977`, :pull:`980`)
+* Added ability for :py:func:`pvlib.soiling.hsu` to accept arbitrary time intervals. (:pull:`980`)
 
 Testing
 ~~~~~~~

From a8aed0138938c34d75b54085db7af233223158be Mon Sep 17 00:00:00 2001
From: Kevin Anderson <kevin.anderson@nrel.gov>
Date: Wed, 26 Aug 2020 18:41:02 -0600
Subject: [PATCH 24/27] remove needs_pandas_22 from test_soiling

---
 pvlib/tests/test_soiling.py | 18 ++++--------------
 1 file changed, 4 insertions(+), 14 deletions(-)

diff --git a/pvlib/tests/test_soiling.py b/pvlib/tests/test_soiling.py
index 76c8fcfe2d..58622f709c 100644
--- a/pvlib/tests/test_soiling.py
+++ b/pvlib/tests/test_soiling.py
@@ -7,8 +7,7 @@
 from pandas.util.testing import assert_series_equal
 from pvlib.soiling import hsu, kimber
 from pvlib.iotools import read_tmy3
-from conftest import (
-    requires_scipy, needs_pandas_0_22, DATA_DIR)
+from conftest import requires_scipy, DATA_DIR
 import pytest
 
 
@@ -30,7 +29,7 @@ def expected_output():
 @pytest.fixture
 def expected_output_1():
     dt = pd.date_range(start=pd.Timestamp(2019, 1, 1, 0, 0, 0),
-        end=pd.Timestamp(2019, 1, 1, 23, 59, 0), freq='1h')
+                       end=pd.Timestamp(2019, 1, 1, 23, 59, 0), freq='1h')
     expected_output_1 = pd.Series(
         data=[0.98484972, 0.97277367, 0.96167471, 0.95119603, 1.,
               0.98484972, 0.97277367, 0.96167471, 1., 1.,
@@ -82,7 +81,6 @@ def rainfall_input():
 
 
 @requires_scipy
-@needs_pandas_0_22
 def test_hsu_no_cleaning(rainfall_input, expected_output):
     """Test Soiling HSU function"""
 
@@ -100,7 +98,6 @@ def test_hsu_no_cleaning(rainfall_input, expected_output):
 
 
 @requires_scipy
-@needs_pandas_0_22
 def test_hsu(rainfall_input, expected_output_2):
     """Test Soiling HSU function with cleanings"""
 
@@ -119,20 +116,17 @@ def test_hsu(rainfall_input, expected_output_2):
 
 
 @requires_scipy
-@needs_pandas_0_22
 def test_hsu_defaults(rainfall_input, expected_output_1):
     """
     Test Soiling HSU function with default deposition velocity and default rain
     accumulation period.
     """
-    result = hsu(
-        rainfall=rainfall_input, cleaning_threshold=0.5, tilt=0.0,
-        pm2_5=1.0e-2,pm10=2.0e-2)
+    result = hsu(rainfall=rainfall_input, cleaning_threshold=0.5, tilt=0.0,
+                 pm2_5=1.0e-2,pm10=2.0e-2)
     assert np.allclose(result.values, expected_output_1)
 
 
 @requires_scipy
-@needs_pandas_0_22
 def test_hsu_variable_time_intervals(rainfall_input, expected_output_3):
     """
     Test Soiling HSU function with variable time intervals.
@@ -165,7 +159,6 @@ def expected_kimber_nowash():
         parse_dates=True, index_col='timestamp')
 
 
-@needs_pandas_0_22
 def test_kimber_nowash(greensboro_rain, expected_kimber_nowash):
     """Test Kimber soiling model with no manual washes"""
     # Greensboro typical expected annual rainfall is 8345mm
@@ -183,7 +176,6 @@ def expected_kimber_manwash():
         parse_dates=True, index_col='timestamp')
 
 
-@needs_pandas_0_22
 def test_kimber_manwash(greensboro_rain, expected_kimber_manwash):
     """Test Kimber soiling model with a manual wash"""
     # a manual wash date
@@ -207,7 +199,6 @@ def expected_kimber_norain():
     return np.where(norain > max_loss_rate, max_loss_rate, norain)
 
 
-@needs_pandas_0_22
 def test_kimber_norain(greensboro_rain, expected_kimber_norain):
     """Test Kimber soiling model with no rain"""
     # a year with no rain
@@ -229,7 +220,6 @@ def expected_kimber_initial_soil():
     return np.where(norain > max_loss_rate, max_loss_rate, norain)
 
 
-@needs_pandas_0_22
 def test_kimber_initial_soil(greensboro_rain, expected_kimber_initial_soil):
     """Test Kimber soiling model with initial soiling"""
     # a year with no rain

From 6cce79775c83ea8ba80004a48bbd8be0b846eb01 Mon Sep 17 00:00:00 2001
From: Kevin Anderson <kevin.anderson@nrel.gov>
Date: Wed, 26 Aug 2020 18:42:46 -0600
Subject: [PATCH 25/27] move time interval note from bug fixes to enhancements

---
 docs/sphinx/source/whatsnew/v0.8.0.rst | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/docs/sphinx/source/whatsnew/v0.8.0.rst b/docs/sphinx/source/whatsnew/v0.8.0.rst
index 0a7c1a0606..361035b8e8 100644
--- a/docs/sphinx/source/whatsnew/v0.8.0.rst
+++ b/docs/sphinx/source/whatsnew/v0.8.0.rst
@@ -52,12 +52,11 @@ Enhancements
 * Added *racking_model*, *module_type*, and *temperature_model_parameters* to
   PVSystem, LocalizedPVSystem, SingleAxisTracker, and
   LocalizedSingleAxisTracker repr methods. (:issue:`1027`)
+* Added ability for :py:func:`pvlib.soiling.hsu` to accept arbitrary time intervals. (:pull:`980`)
 
 Bug fixes
 ~~~~~~~~~
 * Fixed unit and default value errors in :py:func:`pvlib.soiling.hsu`. (:pull:`977`, :pull:`980`)
-* Added ability for :py:func:`pvlib.soiling.hsu` to accept arbitrary time intervals. (:pull:`980`)
-* Fixed unit and default value errors in :py:func:`pvlib.soiling.hsu`. (:pull:`XXX`)
 * Handle NUL characters and fix version column dtype in
   :py:func:`~pvlib.iotools.crn.read_crn`. (:issue:`1025`)
 

From 89b045232532d6eca17727dda046eee703f3a3c9 Mon Sep 17 00:00:00 2001
From: Kevin Anderson <kevin.anderson@nrel.gov>
Date: Wed, 26 Aug 2020 18:45:59 -0600
Subject: [PATCH 26/27] stickler

---
 pvlib/tests/test_soiling.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pvlib/tests/test_soiling.py b/pvlib/tests/test_soiling.py
index 6af40a6121..200bcfe59f 100644
--- a/pvlib/tests/test_soiling.py
+++ b/pvlib/tests/test_soiling.py
@@ -122,7 +122,7 @@ def test_hsu_defaults(rainfall_input, expected_output_1):
     accumulation period.
     """
     result = hsu(rainfall=rainfall_input, cleaning_threshold=0.5, tilt=0.0,
-                 pm2_5=1.0e-2,pm10=2.0e-2)
+                 pm2_5=1.0e-2, pm10=2.0e-2)
     assert np.allclose(result.values, expected_output_1)
 
 

From fb3f71e0080f91cc237b699e6446bb5c3cc9f78b Mon Sep 17 00:00:00 2001
From: Kevin Anderson <kevin.anderson@nrel.gov>
Date: Wed, 26 Aug 2020 19:43:37 -0600
Subject: [PATCH 27/27] review improvements

---
 pvlib/soiling.py | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/pvlib/soiling.py b/pvlib/soiling.py
index 20ceb91215..4e7096b0c6 100644
--- a/pvlib/soiling.py
+++ b/pvlib/soiling.py
@@ -78,15 +78,15 @@ def hsu(rainfall, cleaning_threshold, tilt, pm2_5, pm10,
 
     # determine the time intervals in seconds (dt_sec)
     dt = rainfall.index
-    dt2 = np.roll(dt.copy(), 1)
     # subtract shifted values from original and convert to seconds
-    dt3 = np.delete((dt-dt2), 0).total_seconds()
-    # append last value to end so same number of elements in the array
-    dt_sec = np.append(dt3[0], dt3).astype('float64')
+    dt_diff = (dt[1:] - dt[:-1]).total_seconds()
+    # ensure same number of elements in the array, assuming that the interval
+    # prior to the first value is equal in length to the first interval
+    dt_sec = np.append(dt_diff[0], dt_diff).astype('float64')
 
     horiz_mass_rate = (
         pm2_5 * depo_veloc['2_5'] + np.maximum(pm10 - pm2_5, 0.)
-        * depo_veloc['10']) * dt_sec  # noqa: W503
+        * depo_veloc['10']) * dt_sec
     tilted_mass_rate = horiz_mass_rate * cosd(tilt)  # assuming no rain
 
     # tms -> tilt_mass_rate