Merge pull request #4 from AssessingSolar/add-mad-error-metric

Add mean absolute difference error metric

Author: AdamRJensen

src/solposx/tools.py

@@ -1,6 +1,7 @@
 """Collection of utility functions."""
 
 import pvlib
+import numpy as np
 
 
 def _pandas_to_utc(pd_object):
@@ -39,7 +40,7 @@ def _fractional_hour(times):
 
     Returns
     -------
-    fraction of hour
+    fraction_of_hour : pd.Index
     """
     hour = (times.hour + (
         times.minute + (times.second + times.microsecond*1e-6)/60)/60)
@@ -48,39 +49,44 @@ def _fractional_hour(times):
 
 def calc_error(zenith_1, azimuth_1, zenith_2, azimuth_2):
     """
-    Calculate angular difference metrics between two solar positions.
+    Calculate angular difference metrics between two sets of solar positions.
 
     Parameters
     ----------
     zenith_1, zenith_2 : array-like
-        Zenith angles for the two solar positions. [degrees]
+        Zenith angles for the two sets of solar positions. [degrees]
     azimuth_1, azimuth_2 : array-like
-        Azimuth angles for the two solar positions. [degrees]
+        Azimuth angles for the two sets of solar position. [degrees]
 
     Returns
     -------
     out : dict
         Dict with keys:
 
         * zenith_bias, azimuth_bias: average (signed) difference in zenith/azimuth
+        * zenith_mad, azimuth_mad: mean absolute difference in zenith/azimuth
         * zenith_rmsd, azimuth_rmsd: root-mean-squared difference in zenith/azimuth
         * combined_rmse: total angular root-mean-squared difference in position
     """
     zenith_diff = zenith_1 - zenith_2
     zenith_bias = zenith_diff.mean()
+    zenith_mad = np.abs(zenith_diff).mean()
     zenith_rmsd = (zenith_diff**2).mean()**0.5
 
     azimuth_diff = (azimuth_1 - azimuth_2 + 180) % 360 - 180  # handle 0/360 correctly
     azimuth_bias = azimuth_diff.mean()
+    azimuth_mad = np.abs(azimuth_diff).mean()
     azimuth_rmsd = (azimuth_diff**2).mean()**0.5
 
     aoi = pvlib.irradiance.aoi(zenith_1, azimuth_1, zenith_2, azimuth_2)
     combined_rmsd = (aoi**2).mean()**0.5
 
     out = {
         'zenith_bias': zenith_bias,
+        'zenith_mad': zenith_mad,
         'zenith_rmsd': zenith_rmsd,
         'azimuth_bias': azimuth_bias,
+        'azimuth_mad': azimuth_mad,
         'azimuth_rmsd': azimuth_rmsd,
         'combined_rmsd': combined_rmsd,
     }

tests/test_tools.py

@@ -39,8 +39,10 @@ def expected_calc_error():
     N = 10
     out = {
         'zenith_bias': np.zeros(N),
+        'zenith_mad': np.zeros(N),
         'zenith_rmsd': np.zeros(N),
         'azimuth_bias': np.zeros(N),
+        'azimuth_mad': np.zeros(N),
         'azimuth_rmsd': np.zeros(N),
         'combined_rmsd': np.zeros(N),
     }
@@ -52,3 +54,4 @@ def test_calc_error(expected_calc_error):
     result = calc_error(zeros, zeros, zeros, zeros)
     for k in expected_calc_error.keys():
         np.testing.assert_equal(result[k], expected_calc_error[k])
+    assert len(result.keys()) == len(expected_calc_error.keys())