Merge pull request #1253 from dopplershift/fix-smooth-units

Fix smoothing unit-handling

src/metpy/calc/basic.py

@@ -656,6 +656,7 @@ def sigma_to_pressure(sigma, psfc, ptop):
 
 @exporter.export
 @preprocess_xarray
+@units.wraps('=A', ('=A',))
 def smooth_gaussian(scalar_grid, n):
     """Filter with normal distribution of weights.
 
@@ -742,15 +743,13 @@ def smooth_gaussian(scalar_grid, n):
     # Assume the last two axes represent the horizontal directions
     sgma_seq = [sgma if i > nax - 3 else 0 for i in range(nax)]
 
-    # Compute smoothed field and reattach units
-    res = gaussian_filter(scalar_grid, sgma_seq, truncate=2 * np.sqrt(2))
-    if hasattr(scalar_grid, 'units'):
-        res = res * scalar_grid.units
-    return res
+    # Compute smoothed field
+    return gaussian_filter(scalar_grid, sgma_seq, truncate=2 * np.sqrt(2))
 
 
 @exporter.export
 @preprocess_xarray
+@units.wraps('=A', ('=A',))
 def smooth_n_point(scalar_grid, n=5, passes=1):
     """Filter with normal distribution of weights.
 
@@ -764,8 +763,7 @@ def smooth_n_point(scalar_grid, n=5, passes=1):
         are 5 and 9. Defaults to 5.
 
     passes : int
-        The number of times to apply the filter to the grid. Defaults
-        to 1.
+        The number of times to apply the filter to the grid. Defaults to 1.
 
     Returns
     -------
@@ -782,7 +780,7 @@ def smooth_n_point(scalar_grid, n=5, passes=1):
     masked value or NaN values exists in the array, it will propagate
     to any point that uses that particular grid point in the smoothing
     calculation. Applying the smoothing function multiple times will
-    propogate NaNs further throughout the domain.
+    propagate NaNs further throughout the domain.
 
     """
     if n == 9:

src/metpy/testing.py

@@ -131,6 +131,17 @@ def check_and_drop_units(actual, desired):
     return actual, desired
 
 
+def check_mask(actual, desired):
+    """Check that two arrays have the same mask.
+
+    This handles the fact that `~numpy.testing.assert_array_equal` ignores masked values
+    in either of the arrays. This ensures that the masks are identical.
+    """
+    actual_mask = getattr(actual, 'mask', np.full(np.asarray(actual).shape, False))
+    desired_mask = getattr(desired, 'mask', np.full(np.asarray(desired).shape, False))
+    np.testing.assert_array_equal(actual_mask, desired_mask)
+
+
 def assert_nan(value, units):
     """Check for nan with proper units."""
     value, _ = check_and_drop_units(value, np.nan * units)
@@ -152,6 +163,7 @@ def assert_array_almost_equal(actual, desired, decimal=7):
     Wrapper around :func:`numpy.testing.assert_array_almost_equal`
     """
     actual, desired = check_and_drop_units(actual, desired)
+    check_mask(actual, desired)
     numpy.testing.assert_array_almost_equal(actual, desired, decimal)
 
 
@@ -161,6 +173,7 @@ def assert_array_equal(actual, desired):
     Wrapper around :func:`numpy.testing.assert_array_equal`
     """
     actual, desired = check_and_drop_units(actual, desired)
+    check_mask(actual, desired)
     numpy.testing.assert_array_equal(actual, desired)
 
 

tests/calc/test_basic.py

@@ -165,10 +165,9 @@ def test_windchill_invalid():
 
     wc = windchill(temp, speed)
     # We don't care about the masked values
-    truth = np.array([2.6230789, np.nan, np.nan, np.nan, np.nan, np.nan]) * units.degF
-    mask = np.array([False, True, True, True, True, True])
+    truth = np.ma.array([2.6230789, np.nan, np.nan, np.nan, np.nan, np.nan],
+                        mask=[False, True, True, True, True, True]) * units.degF
     assert_array_almost_equal(truth, wc)
-    assert_array_equal(wc.mask, mask)
 
 
 def test_windchill_undefined_flag():
@@ -249,7 +248,7 @@ def test_heat_index_vs_nws():
     temp = units.Quantity(np.array([86, 111, 40, 96]), units.degF)
     rh = np.ma.array([45, 27, 99, 60]) * units.percent
     hi = heat_index(temp, rh)
-    truth = units.Quantity(np.ma.array([87, 121, 40, 116]), units.degF)
+    truth = np.ma.array([87, 121, 40, 116], mask=[False, False, True, False]) * units.degF
     assert_array_almost_equal(hi, truth, 0)
 
 
@@ -413,8 +412,9 @@ def test_apparent_temperature():
                              [10, 10, 10]]) * units.percent
     wind = np.array([[5, 3, 3],
                      [10, 1, 10]]) * units.mph
-    truth = np.array([[99.6777178, 86.3357671, 70],
-                      [8.8140662, 20, 60]]) * units.degF
+    truth = np.ma.array([[99.6777178, 86.3357671, 70],
+                         [8.8140662, 20, 60]],
+                        mask=[[False, False, True], [False, True, True]]) * units.degF
     res = apparent_temperature(temperature, rel_humidity, wind)
     assert_array_almost_equal(res, truth, 6)
 
@@ -589,24 +589,58 @@ def test_smooth_n_pt_9_repeat():
                     [5816., 5784., 5744., 5716., 5684.]])
     shght = smooth_n_point(hght, 9, 2)
     s_true = np.array([[5640., 5640., 5640., 5640., 5640.],
-                      [5684., 5675.4375, 5666.9375, 5658.8125, 5651.],
-                      [5728., 5710.875, 5693.875, 5677.625, 5662.],
-                      [5772., 5746.375, 5720.625, 5696.375, 5673.],
-                      [5816., 5784., 5744., 5716., 5684.]])
+                       [5684., 5675.4375, 5666.9375, 5658.8125, 5651.],
+                       [5728., 5710.875, 5693.875, 5677.625, 5662.],
+                       [5772., 5746.375, 5720.625, 5696.375, 5673.],
+                       [5816., 5784., 5744., 5716., 5684.]])
     assert_array_almost_equal(shght, s_true)
 
 
 def test_smooth_n_pt_wrong_number():
     """Test the smooth_n_pt function using wrong number of points."""
     hght = np.array([[5640., 5640., 5640., 5640., 5640.],
-                    [5684., 5676., 5666., 5659., 5651.],
-                    [5728., 5712., 5692., 5678., 5662.],
-                    [5772., 5748., 5718., 5697., 5673.],
-                    [5816., 5784., 5744., 5716., 5684.]])
+                     [5684., 5676., 5666., 5659., 5651.],
+                     [5728., 5712., 5692., 5678., 5662.],
+                     [5772., 5748., 5718., 5697., 5673.],
+                     [5816., 5784., 5744., 5716., 5684.]])
     with pytest.raises(ValueError):
         smooth_n_point(hght, 7)
 
 
+def test_smooth_n_pt_temperature():
+    """Test the smooth_n_pt function with temperature units."""
+    t = np.array([[2.73, 3.43, 6.53, 7.13, 4.83],
+                  [3.73, 4.93, 6.13, 6.63, 8.23],
+                  [3.03, 4.83, 6.03, 7.23, 7.63],
+                  [3.33, 4.63, 7.23, 6.73, 6.23],
+                  [3.93, 3.03, 7.43, 9.23, 9.23]]) * units.degC
+
+    smooth_t = smooth_n_point(t, 9, 1)
+    smooth_t_true = np.array([[2.73, 3.43, 6.53, 7.13, 4.83],
+                              [3.73, 4.6425, 5.96125, 6.81124, 8.23],
+                              [3.03, 4.81125, 6.1175, 6.92375, 7.63],
+                              [3.33, 4.73625, 6.43, 7.3175, 6.23],
+                              [3.93, 3.03, 7.43, 9.23, 9.23]]) * units.degC
+    assert_array_almost_equal(smooth_t, smooth_t_true, 4)
+
+
+def test_smooth_gaussian_temperature():
+    """Test the smooth_gaussian function with temperature units."""
+    t = np.array([[2.73, 3.43, 6.53, 7.13, 4.83],
+                  [3.73, 4.93, 6.13, 6.63, 8.23],
+                  [3.03, 4.83, 6.03, 7.23, 7.63],
+                  [3.33, 4.63, 7.23, 6.73, 6.23],
+                  [3.93, 3.03, 7.43, 9.23, 9.23]]) * units.degC
+
+    smooth_t = smooth_gaussian(t, 3)
+    smooth_t_true = np.array([[2.8892, 3.7657, 6.2805, 6.8532, 5.3174],
+                              [3.6852, 4.799, 6.0844, 6.7816, 7.7617],
+                              [3.2762, 4.787, 6.117, 7.0792, 7.5181],
+                              [3.4618, 4.6384, 6.886, 6.982, 6.6653],
+                              [3.8115, 3.626, 7.1705, 8.8528, 8.9605]]) * units.degC
+    assert_array_almost_equal(smooth_t, smooth_t_true, 4)
+
+
 def test_altimeter_to_station_pressure_inhg():
     """Test the altimeter to station pressure function with inches of mercury."""
     altim = 29.8 * units.inHg

tests/test_testing.py

@@ -0,0 +1,24 @@
+#  Copyright (c) 2019 MetPy Developers.
+#  Distributed under the terms of the BSD 3-Clause License.
+#  SPDX-License-Identifier: BSD-3-Clause
+"""Test MetPy's testing utilities."""
+
+import numpy as np
+import pytest
+
+from metpy.testing import assert_array_almost_equal
+
+
+# Test #1183: numpy.testing.assert_array* ignores any masked value, so work-around
+def test_masked_arrays():
+    """Test that we catch masked arrays with different masks."""
+    with pytest.raises(AssertionError):
+        assert_array_almost_equal(np.array([10, 20]),
+                                  np.ma.array([10, np.nan], mask=[False, True]), 2)
+
+
+def test_masked_and_no_mask():
+    """Test that we can compare a masked array with no masked values and a regular array."""
+    a = np.array([10, 20])
+    b = np.ma.array([10, 20], mask=[False, False])
+    assert_array_almost_equal(a, b)