scikit-learn · rth · Jul 4, 2020 · Sep 18, 2019 · Sep 18, 2019 · Sep 18, 2019
diff --git a/doc/modules/classes.rst b/doc/modules/classes.rst
@@ -900,7 +900,7 @@ Miscellaneous
     manifold.smacof
     manifold.spectral_embedding
     manifold.trustworthiness
-	
+
 
 .. _metrics_ref:
 
@@ -981,6 +981,7 @@ details.
    metrics.mean_squared_error
    metrics.mean_squared_log_error
    metrics.median_absolute_error
+   metrics.mean_absolute_percentage_error
    metrics.r2_score
    metrics.mean_poisson_deviance
    metrics.mean_gamma_deviance

diff --git a/doc/modules/model_evaluation.rst b/doc/modules/model_evaluation.rst
@@ -54,51 +54,52 @@ the model and the data, like :func:`metrics.mean_squared_error`, are
 available as neg_mean_squared_error which return the negated value
 of the metric.
 
-==============================    =============================================     ==================================
-Scoring                           Function                                          Comment
-==============================    =============================================     ==================================
+====================================   ==============================================     ==================================
+Scoring                                Function                                           Comment
+====================================   ==============================================     ==================================
 **Classification**
-'accuracy'                        :func:`metrics.accuracy_score`
-'balanced_accuracy'               :func:`metrics.balanced_accuracy_score`
-'average_precision'               :func:`metrics.average_precision_score`
-'neg_brier_score'                 :func:`metrics.brier_score_loss`
-'f1'                              :func:`metrics.f1_score`                          for binary targets
-'f1_micro'                        :func:`metrics.f1_score`                          micro-averaged
-'f1_macro'                        :func:`metrics.f1_score`                          macro-averaged
-'f1_weighted'                     :func:`metrics.f1_score`                          weighted average
-'f1_samples'                      :func:`metrics.f1_score`                          by multilabel sample
-'neg_log_loss'                    :func:`metrics.log_loss`                          requires ``predict_proba`` support
-'precision' etc.                  :func:`metrics.precision_score`                   suffixes apply as with 'f1'
-'recall' etc.                     :func:`metrics.recall_score`                      suffixes apply as with 'f1'
-'jaccard' etc.                    :func:`metrics.jaccard_score`                     suffixes apply as with 'f1'
-'roc_auc'                         :func:`metrics.roc_auc_score`
-'roc_auc_ovr'                     :func:`metrics.roc_auc_score`
-'roc_auc_ovo'                     :func:`metrics.roc_auc_score`
-'roc_auc_ovr_weighted'            :func:`metrics.roc_auc_score`
-'roc_auc_ovo_weighted'            :func:`metrics.roc_auc_score`
+'accuracy'                             :func:`metrics.accuracy_score`
+'balanced_accuracy'                    :func:`metrics.balanced_accuracy_score`
+'average_precision'                    :func:`metrics.average_precision_score`
+'neg_brier_score'                      :func:`metrics.brier_score_loss`
+'f1'                                   :func:`metrics.f1_score`                           for binary targets
+'f1_micro'                             :func:`metrics.f1_score`                           micro-averaged
+'f1_macro'                             :func:`metrics.f1_score`                           macro-averaged
+'f1_weighted'                          :func:`metrics.f1_score`                           weighted average
+'f1_samples'                           :func:`metrics.f1_score`                           by multilabel sample
+'neg_log_loss'                         :func:`metrics.log_loss`                           requires ``predict_proba`` support
+'precision' etc.                       :func:`metrics.precision_score`                    suffixes apply as with 'f1'
+'recall' etc.                          :func:`metrics.recall_score`                       suffixes apply as with 'f1'
+'jaccard' etc.                         :func:`metrics.jaccard_score`                      suffixes apply as with 'f1'
+'roc_auc'                              :func:`metrics.roc_auc_score`
+'roc_auc_ovr'                          :func:`metrics.roc_auc_score`
+'roc_auc_ovo'                          :func:`metrics.roc_auc_score`
+'roc_auc_ovr_weighted'                 :func:`metrics.roc_auc_score`
+'roc_auc_ovo_weighted'                 :func:`metrics.roc_auc_score`
 
 **Clustering**
-'adjusted_mutual_info_score'      :func:`metrics.adjusted_mutual_info_score`
-'adjusted_rand_score'             :func:`metrics.adjusted_rand_score`
-'completeness_score'              :func:`metrics.completeness_score`
-'fowlkes_mallows_score'           :func:`metrics.fowlkes_mallows_score`
-'homogeneity_score'               :func:`metrics.homogeneity_score`
-'mutual_info_score'               :func:`metrics.mutual_info_score`
-'normalized_mutual_info_score'    :func:`metrics.normalized_mutual_info_score`
-'v_measure_score'                 :func:`metrics.v_measure_score`
+'adjusted_mutual_info_score'           :func:`metrics.adjusted_mutual_info_score`
+'adjusted_rand_score'                  :func:`metrics.adjusted_rand_score`
+'completeness_score'                   :func:`metrics.completeness_score`
+'fowlkes_mallows_score'                :func:`metrics.fowlkes_mallows_score`
+'homogeneity_score'                    :func:`metrics.homogeneity_score`
+'mutual_info_score'                    :func:`metrics.mutual_info_score`
+'normalized_mutual_info_score'         :func:`metrics.normalized_mutual_info_score`
+'v_measure_score'                      :func:`metrics.v_measure_score`
 
 **Regression**
-'explained_variance'              :func:`metrics.explained_variance_score`
-'max_error'                       :func:`metrics.max_error`
-'neg_mean_absolute_error'         :func:`metrics.mean_absolute_error`
-'neg_mean_squared_error'          :func:`metrics.mean_squared_error`
-'neg_root_mean_squared_error'     :func:`metrics.mean_squared_error`
-'neg_mean_squared_log_error'      :func:`metrics.mean_squared_log_error`
-'neg_median_absolute_error'       :func:`metrics.median_absolute_error`
-'r2'                              :func:`metrics.r2_score`
-'neg_mean_poisson_deviance'       :func:`metrics.mean_poisson_deviance`
-'neg_mean_gamma_deviance'         :func:`metrics.mean_gamma_deviance`
-==============================    =============================================     ==================================
+'explained_variance'                   :func:`metrics.explained_variance_score`
+'max_error'                            :func:`metrics.max_error`
+'neg_mean_absolute_error'              :func:`metrics.mean_absolute_error`
+'neg_mean_squared_error'               :func:`metrics.mean_squared_error`
+'neg_root_mean_squared_error'          :func:`metrics.mean_squared_error`
+'neg_mean_squared_log_error'           :func:`metrics.mean_squared_log_error`
+'neg_median_absolute_error'            :func:`metrics.median_absolute_error`
+'r2'                                   :func:`metrics.r2_score`
+'neg_mean_poisson_deviance'            :func:`metrics.mean_poisson_deviance`
+'neg_mean_gamma_deviance'              :func:`metrics.mean_gamma_deviance`
+'neg_mean_absolute_percentage_error'   :func:`metrics.mean_absolute_percentage_error`
+====================================   ==============================================     ==================================
 
 
 Usage examples:
@@ -1963,6 +1964,42 @@ function::
   >>> mean_squared_log_error(y_true, y_pred)
   0.044...
 
+.. _mean_absolute_percentage_error:
+
+Mean absolute percentage error
+------------------------------
+The :func:`mean_absolute_percentage_error` (MAPE), also known as mean absolute
+percentage deviation (MAPD), is an evaluation metric for regression problems.
+The idea of this metric is to be sensitive to relative errors. It is for example
+not changed by a global scaling of the target variable.
+
+If :math:`\hat{y}_i` is the predicted value of the :math:`i`-th sample
+and :math:`y_i` is the corresponding true value, then the mean absolute percentage
+error (MAPE) estimated over :math:`n_{\text{samples}}` is defined as
+
+.. math::
+
+  \text{MAPE}(y, \hat{y}) = \frac{1}{n_{\text{samples}}} \sum_{i=0}^{n_{\text{samples}}-1} \frac{{}\left| y_i - \hat{y}_i \right|}{max(\epsilon, \left| y_i \right|)}
+
+where :math:`\epsilon` is an arbitrary small yet strictly positive number to
+avoid undefined results when y is zero.
+
+The :func:`mean_absolute_percentage_error` function supports multioutput.
+
+Here is a small example of usage of the :func:`mean_absolute_percentage_error`
+function::
+
+  >>> from sklearn.metrics import mean_absolute_percentage_error
+  >>> y_true = [1, 10, 1e6]
+  >>> y_pred = [0.9, 15, 1.2e6]
+  >>> mean_absolute_percentage_error(y_true, y_pred)
+  0.2666...
+
+In above example, if we had used `mean_absolute_error`, it would have ignored
+the small magnitude values and only reflected the error in prediction of highest
+magnitude value. But that problem is resolved in case of MAPE because it calculates
+relative percentage error with respect to actual output.
+
 .. _median_absolute_error:
 
 Median absolute error

diff --git a/doc/whats_new/_contributors.rst b/doc/whats_new/_contributors.rst
@@ -176,4 +176,4 @@
 
 .. _Nicolas Hug: https://github.com/NicolasHug
 
-.. _Guillaume Lemaitre: https://github.com/glemaitre
+.. _Guillaume Lemaitre: https://github.com/glemaitre
diff --git a/doc/whats_new/v0.24.rst b/doc/whats_new/v0.24.rst
@@ -150,6 +150,12 @@ Changelog
 :mod:`sklearn.metrics`
 ......................
 
+- |Feature| Added :func:`metrics.mean_absolute_percentage_error` metric and
+  the associated scorer for regression problems. :issue:`10708` fixed with the
+  PR :pr:`15007` by :user:`Ashutosh Hathidara <ashutosh1919>`. The scorer and
+  some practical test cases were taken from PR :pr:`10711` by
+  :user:`Mohamed Ali Jamaoui <mohamed-ali>`.
+
 - |Fix| Fixed a bug in :func:`metrics.mean_squared_error` where the
   average of multiple RMSE values was incorrectly calculated as the root of the
   average of multiple MSE values.

diff --git a/sklearn/metrics/__init__.py b/sklearn/metrics/__init__.py
@@ -64,6 +64,7 @@
 from ._regression import mean_squared_error
 from ._regression import mean_squared_log_error
 from ._regression import median_absolute_error
+from ._regression import mean_absolute_percentage_error
 from ._regression import r2_score
 from ._regression import mean_tweedie_deviance
 from ._regression import mean_poisson_deviance
@@ -128,6 +129,7 @@
     'mean_gamma_deviance',
     'mean_tweedie_deviance',
     'median_absolute_error',
+    'mean_absolute_percentage_error',
     'multilabel_confusion_matrix',
     'mutual_info_score',
     'ndcg_score',

diff --git a/sklearn/metrics/_regression.py b/sklearn/metrics/_regression.py
@@ -20,6 +20,7 @@
 #          Michael Eickenberg <[email protected]>
 #          Konstantin Shmelkov <[email protected]>
 #          Christian Lorentzen <[email protected]>
+#          Ashutosh Hathidara <[email protected]>
 # License: BSD 3 clause
 
 import numpy as np
@@ -41,6 +42,7 @@
     "mean_squared_error",
     "mean_squared_log_error",
     "median_absolute_error",
+    "mean_absolute_percentage_error",
     "r2_score",
     "explained_variance_score",
     "mean_tweedie_deviance",
@@ -192,6 +194,81 @@ def mean_absolute_error(y_true, y_pred, *,
     return np.average(output_errors, weights=multioutput)
 
 
+def mean_absolute_percentage_error(y_true, y_pred,
+                                   sample_weight=None,
+                                   multioutput='uniform_average'):
+    """Mean absolute percentage error regression loss
+
+    Note here that we do not represent the output as a percentage in range
+    [0, 100]. Instead, we represent it in range [0, 1/eps]. Read more in the
+    :ref:`User Guide <mean_absolute_percentage_error>`.
+
+    Parameters
+    ----------
+    y_true : array-like of shape (n_samples,) or (n_samples, n_outputs)
+        Ground truth (correct) target values.
+
+    y_pred : array-like of shape (n_samples,) or (n_samples, n_outputs)
+        Estimated target values.
+
+    sample_weight : array-like of shape (n_samples,), default=None
+        Sample weights.
+
+    multioutput : {'raw_values', 'uniform_average'} or array-like
+        Defines aggregating of multiple output values.
+        Array-like value defines weights used to average errors.
+        If input is list then the shape must be (n_outputs,).
+
+        'raw_values' :
+            Returns a full set of errors in case of multioutput input.
+
+        'uniform_average' :
+            Errors of all outputs are averaged with uniform weight.
+
+    Returns
+    -------
+    loss : float or ndarray of floats in the range [0, 1/eps]
+        If multioutput is 'raw_values', then mean absolute percentage error
+        is returned for each output separately.
+        If multioutput is 'uniform_average' or an ndarray of weights, then the
+        weighted average of all output errors is returned.
+
+        MAPE output is non-negative floating point. The best value is 0.0.
+        But note the fact that bad predictions can lead to arbitarily large
+        MAPE values, especially if some y_true values are very close to zero.
+        Note that we return a large value instead of `inf` when y_true is zero.
+
+    Examples
+    --------
+    >>> from sklearn.metrics import mean_absolute_percentage_error
+    >>> y_true = [3, -0.5, 2, 7]
+    >>> y_pred = [2.5, 0.0, 2, 8]
+    >>> mean_absolute_percentage_error(y_true, y_pred)
+    0.3273...
+    >>> y_true = [[0.5, 1], [-1, 1], [7, -6]]
+    >>> y_pred = [[0, 2], [-1, 2], [8, -5]]
+    >>> mean_absolute_percentage_error(y_true, y_pred)
+    0.5515...
+    >>> mean_absolute_percentage_error(y_true, y_pred, multioutput=[0.3, 0.7])
+    0.6198...
+    """
+    y_type, y_true, y_pred, multioutput = _check_reg_targets(
+        y_true, y_pred, multioutput)
+    check_consistent_length(y_true, y_pred, sample_weight)
+    epsilon = np.finfo(np.float64).eps
+    mape = np.abs(y_pred - y_true) / np.maximum(np.abs(y_true), epsilon)
+    output_errors = np.average(mape,
+                               weights=sample_weight, axis=0)
+    if isinstance(multioutput, str):
+        if multioutput == 'raw_values':
+            return output_errors
+        elif multioutput == 'uniform_average':
+            # pass None as weights to np.average: uniform mean
+            multioutput = None
+
+    return np.average(output_errors, weights=multioutput)
+
+
 @_deprecate_positional_args
 def mean_squared_error(y_true, y_pred, *,
                        sample_weight=None,

diff --git a/sklearn/metrics/_scorer.py b/sklearn/metrics/_scorer.py
@@ -30,7 +30,7 @@
                f1_score, roc_auc_score, average_precision_score,
                precision_score, recall_score, log_loss,
                balanced_accuracy_score, explained_variance_score,
-               brier_score_loss, jaccard_score)
+               brier_score_loss, jaccard_score, mean_absolute_percentage_error)
 
 from .cluster import adjusted_rand_score
 from .cluster import homogeneity_score
@@ -614,6 +614,9 @@ def make_scorer(score_func, *, greater_is_better=True, needs_proba=False,
                                                 greater_is_better=False)
 neg_mean_absolute_error_scorer = make_scorer(mean_absolute_error,
                                              greater_is_better=False)
+neg_mean_absolute_percentage_error_scorer = make_scorer(
+    mean_absolute_percentage_error, greater_is_better=False
+)
 neg_median_absolute_error_scorer = make_scorer(median_absolute_error,
                                                greater_is_better=False)
 neg_root_mean_squared_error_scorer = make_scorer(mean_squared_error,
@@ -674,6 +677,7 @@ def make_scorer(score_func, *, greater_is_better=True, needs_proba=False,
                max_error=max_error_scorer,
                neg_median_absolute_error=neg_median_absolute_error_scorer,
                neg_mean_absolute_error=neg_mean_absolute_error_scorer,
+               neg_mean_absolute_percentage_error=neg_mean_absolute_percentage_error_scorer,  # noqa
                neg_mean_squared_error=neg_mean_squared_error_scorer,
                neg_mean_squared_log_error=neg_mean_squared_log_error_scorer,
                neg_root_mean_squared_error=neg_root_mean_squared_error_scorer,

diff --git a/sklearn/metrics/tests/test_common.py b/sklearn/metrics/tests/test_common.py
@@ -41,6 +41,7 @@
 from sklearn.metrics import max_error
 from sklearn.metrics import matthews_corrcoef
 from sklearn.metrics import mean_absolute_error
+from sklearn.metrics import mean_absolute_percentage_error
 from sklearn.metrics import mean_squared_error
 from sklearn.metrics import mean_tweedie_deviance
 from sklearn.metrics import mean_poisson_deviance
@@ -98,6 +99,7 @@
     "mean_absolute_error": mean_absolute_error,
     "mean_squared_error": mean_squared_error,
     "median_absolute_error": median_absolute_error,
+    "mean_absolute_percentage_error": mean_absolute_percentage_error,
     "explained_variance_score": explained_variance_score,
     "r2_score": partial(r2_score, multioutput='variance_weighted'),
     "mean_normal_deviance": partial(mean_tweedie_deviance, power=0),
@@ -425,7 +427,7 @@ def precision_recall_curve_padded_thresholds(*args, **kwargs):
 # Regression metrics with "multioutput-continuous" format support
 MULTIOUTPUT_METRICS = {
     "mean_absolute_error", "median_absolute_error", "mean_squared_error",
-    "r2_score", "explained_variance_score"
+    "r2_score", "explained_variance_score", "mean_absolute_percentage_error"
 }
 
 # Symmetric with respect to their input arguments y_true and y_pred
@@ -472,7 +474,7 @@ def precision_recall_curve_padded_thresholds(*args, **kwargs):
     "macro_f0.5_score", "macro_f2_score", "macro_precision_score",
     "macro_recall_score", "log_loss", "hinge_loss",
     "mean_gamma_deviance", "mean_poisson_deviance",
-    "mean_compound_poisson_deviance"
+    "mean_compound_poisson_deviance", "mean_absolute_percentage_error"
 }
 
 
@@ -1371,7 +1373,15 @@ def test_thresholded_multilabel_multioutput_permutations_invariance(name):
         y_true_perm = y_true[:, perm]
 
         current_score = metric(y_true_perm, y_score_perm)
-        assert_almost_equal(score, current_score)
+        if metric == mean_absolute_percentage_error:
+            assert np.isfinite(current_score)
+            assert current_score > 1e6
+            # Here we are not comparing the values in case of MAPE because
+            # whenever y_true value is exactly zero, the MAPE value doesn't
+            # signify anything. Thus, in this case we are just expecting
+            # very large finite value.
+        else:
+            assert_almost_equal(score, current_score)
 
 
 @pytest.mark.parametrize(
Original file line number	Diff line number	Diff line change
Expand Up		@@ -176,4 +176,4 @@

		.. _Nicolas Hug: https://github.com/NicolasHug

		.. _Guillaume Lemaitre: https://github.com/glemaitre
		.. _Guillaume Lemaitre: https://github.com/glemaitre