Fix/metrics

darts/metrics/metrics.py

@@ -286,9 +286,57 @@ def mape(actual_series: TimeSeries,
     return 100. * np.mean(np.abs((y_true - y_hat) / y_true))
 
 
+@multivariate_support
+def smape(actual_series: TimeSeries,
+          pred_series: TimeSeries,
+          intersect: bool = True,
+          reduction: Callable[[np.ndarray], float] = np.mean) -> float:
+    """ symmetric Mean Absolute Percentage Error (sMAPE).
+
+    Given a time series of actual values :math:`y_t` and a time series of predicted values :math:`\\hat{y}_t`
+    both of length :math:`T`, it is a percentage value computed as
+
+    .. math::
+        200 \\cdot \\frac{1}{T}
+        \\sum_{t=1}^{T}{\\frac{\\left| y_t - \\hat{y}_t \\right|}{\\left| y_t \\right| + \\left| \\hat{y}_t \\right|} }.
+
+    Note that it will raise a `ValueError` if :math:`\\left| y_t \\right| + \\left| \\hat{y}_t \\right| = 0`
+     for some :math:`t`. Consider using the Mean Absolute Scaled Error (MASE) in these cases.
+
+    Parameters
+    ----------
+    actual_series
+        The series of actual values
+    pred_series
+        The series of predicted values
+    intersect
+        For time series that are overlapping in time without having the same time index, setting `intersect=True`
+        will consider the values only over their common time interval (intersection in time).
+    reduction
+        Function taking as input a np.ndarray and returning a scalar value. This function is used to aggregate
+        the metrics of different components in case of multivariate TimeSeries instances.
+
+    Raises
+    ------
+    ValueError
+        If the actual series and the pred series contains some zeros at the same time index.
+
+    Returns
+    -------
+    float
+        The symmetric Mean Absolute Percentage Error (sMAPE)
+    """
+
+    y_true, y_hat = _get_values_or_raise(actual_series, pred_series, intersect)
+    raise_if_not(np.logical_or(y_true != 0, y_hat != 0).all(),
+                 'The actual series must be strictly positive to compute the sMAPE.', logger)
+    return 200. * np.mean(np.abs((y_true - y_hat) / (np.abs(y_true) + np.abs(y_hat))))
+
+
 @multivariate_support
 def mase(actual_series: TimeSeries,
          pred_series: TimeSeries,
+         insample: TimeSeries,
          m: Optional[int] = 1,
          intersect: bool = True,
          reduction: Callable[[np.ndarray], float] = np.mean) -> float:
@@ -303,6 +351,9 @@ def mase(actual_series: TimeSeries,
         The series of actual values
     pred_series
         The series of predicted values
+    insample
+        The prior series used to forecast `pred_series` .
+        A naive forecast method is used to compute the scale of the data.
     m
         Optionally, the seasonality to use for differencing.
         `m=1` corresponds to the non-seasonal MASE, whereas `m>1` corresponds to seasonal MASE.
@@ -315,23 +366,30 @@ def mase(actual_series: TimeSeries,
         Function taking as input a np.ndarray and returning a scalar value. This function is used to aggregate
         the metrics of different components in case of multivariate TimeSeries instances.
 
+    Raises
+    ------
+    ValueError
+        If the `insample` series is periodic ( :math:`X_t = X_{t-m}` )
+
     Returns
     -------
     float
         The Mean Absolute Scaled Error (MASE)
     """
 
+    raise_if_not(insample.end_time() + insample.freq() == pred_series.start_time(),
+                 "The pred_series must be the forecast of the insample series", logger)
     if m is None:
-        test_season, m = check_seasonality(actual_series)
+        test_season, m = check_seasonality(insample)
         if not test_season:
             warn("No seasonality found when computing MASE. Fixing the period to 1.", UserWarning)
             m = 1
     y_true, y_hat = _get_values_or_raise(actual_series, pred_series, intersect)
-    errors = np.sum(np.abs(y_true - y_hat))
-    t = y_true.size
-    scale = t / (t - m) * np.sum(np.abs(y_true[m:] - y_true[:-m]))
+    x_t = insample.values()
+    errors = np.abs(y_true - y_hat)
+    scale = np.mean(np.abs(x_t[m:] - x_t[:-m]))
     raise_if_not(not np.isclose(scale, 0), "cannot use MASE with periodical signals", logger)
-    return errors / scale
+    return np.mean(errors / scale)
 
 
 @multivariate_support

darts/tests/test_metrics.py

@@ -9,9 +9,11 @@
 
 class MetricsTestCase(unittest.TestCase):
 
+    pd_train = pd.Series(np.sin(np.pi * np.arange(31) / 4) + 1, index=pd.date_range('20121201', '20121231'))
     pd_series1 = pd.Series(range(10), index=pd.date_range('20130101', '20130110'))
     pd_series2 = pd.Series(np.random.rand(10) * 10 + 1, index=pd.date_range('20130101', '20130110'))
     pd_series3 = pd.Series(np.sin(np.pi * np.arange(20) / 4) + 1, index=pd.date_range('20130101', '20130120'))
+    series_train = TimeSeries.from_series(pd_train)
     series1: TimeSeries = TimeSeries.from_series(pd_series1)
     pd_series1[:] = pd_series1.mean()
     series0: TimeSeries = TimeSeries.from_series(pd_series1)
@@ -30,15 +32,22 @@ def test_zero(self):
         with self.assertRaises(ValueError):
             metrics.mape(self.series1, self.series1)
 
+        with self.assertRaises(ValueError):
+            metrics.smape(self.series1, self.series1)
+
         with self.assertRaises(ValueError):
             metrics.mape(self.series12, self.series12)
 
+        with self.assertRaises(ValueError):
+            metrics.smape(self.series12, self.series12)
+
         with self.assertRaises(ValueError):
             metrics.ope(self.series1 - self.series1.pd_series().mean(), self.series1 - self.series1.pd_series().mean())
 
     def test_same(self):
         self.assertEqual(metrics.mape(self.series1 + 1, self.series1 + 1), 0)
-        self.assertEqual(metrics.mase(self.series1 + 1, self.series1 + 1, 1), 0)
+        self.assertEqual(metrics.smape(self.series1 + 1, self.series1 + 1), 0)
+        self.assertEqual(metrics.mase(self.series1 + 1, self.series1 + 1, self.series_train, 1), 0)
         self.assertEqual(metrics.marre(self.series1 + 1, self.series1 + 1), 0)
         self.assertEqual(metrics.r2_score(self.series1 + 1, self.series1 + 1), 1)
         self.assertEqual(metrics.ope(self.series1 + 1, self.series1 + 1), 0)
@@ -47,15 +56,15 @@ def helper_test_shape_equality(self, metric):
         self.assertAlmostEqual(metric(self.series12, self.series21),
                                metric(self.series1.append(self.series2b), self.series2.append(self.series1b)))
 
-    def helper_test_multivariate_duplication_equality(self, metric):
+    def helper_test_multivariate_duplication_equality(self, metric, **kwargs):
         series11 = self.series1.stack(self.series1) + 1
         series22 = self.series2.stack(self.series2)
         series33 = self.series3.stack(self.series3)
-        self.assertAlmostEqual(metric(series11, series22), metric(self.series1 + 1, self.series2))
-        self.assertAlmostEqual(metric(series11, series33), metric(self.series1 + 1, self.series3))
-        self.assertAlmostEqual(metric(series22, series33), metric(self.series2, self.series3))
-        self.assertAlmostEqual(metric(series22, series33, reduction=(lambda x: x[0])),
-                               metric(self.series2, self.series3, reduction=(lambda x: x[0])))
+        self.assertAlmostEqual(metric(series11, series22, **kwargs), metric(self.series1 + 1, self.series2, **kwargs))
+        self.assertAlmostEqual(metric(series11, series33, **kwargs), metric(self.series1 + 1, self.series3, **kwargs))
+        self.assertAlmostEqual(metric(series22, series33, **kwargs), metric(self.series2, self.series3, **kwargs))
+        self.assertAlmostEqual(metric(series22, series33, reduction=(lambda x: x[0]), **kwargs),
+                               metric(self.series2, self.series3, reduction=(lambda x: x[0]), **kwargs))
 
     def test_r2(self):
         from sklearn.metrics import r2_score
@@ -71,7 +80,7 @@ def test_marre(self):
 
     def test_season(self):
         with self.assertRaises(ValueError):
-            metrics.mase(self.series3, self.series3 * 1.3, 8)
+            metrics.mase(self.series3, self.series3 * 1.3, self.series_train, 8)
 
     def test_mse(self):
         self.helper_test_shape_equality(metrics.mse)
@@ -94,8 +103,14 @@ def test_coefficient_of_variation(self):
     def test_mape(self):
         self.helper_test_multivariate_duplication_equality(metrics.mape)
 
+    def test_smape(self):
+        self.helper_test_multivariate_duplication_equality(metrics.smape)
+
     def test_mase(self):
-        self.helper_test_multivariate_duplication_equality(metrics.mase)
+        self.helper_test_multivariate_duplication_equality(metrics.mase, insample=self.series_train)
+
+        with self.assertRaises(ValueError):
+            metrics.mase(self.series1, self.series2, self.series3, 1)
 
     def test_ope(self):
         self.helper_test_multivariate_duplication_equality(metrics.ope)