[ENH] Enable multitarget problem types for OWTestAndScore and OWPredictions

Orange/base.py

@@ -3,12 +3,12 @@
 from collections.abc import Iterable
 import re
 import warnings
-from typing import Callable, Dict
+from typing import Callable, Dict, Optional
 
 import numpy as np
 import scipy
 
-from Orange.data import Table, Storage, Instance, Value
+from Orange.data import Table, Storage, Instance, Value, Domain
 from Orange.data.filter import HasClass
 from Orange.data.table import DomainTransformationError
 from Orange.data.util import one_hot
@@ -86,6 +86,9 @@ class Learner(ReprableWithPreprocessors):
     #: A sequence of data preprocessors to apply on data prior to
     #: fitting the model
     preprocessors = ()
+
+    # Note: Do not use this class attribute.
+    #       It remains here for compatibility reasons.
     learner_adequacy_err_msg = ''
 
     def __init__(self, preprocessors=None):
@@ -95,6 +98,7 @@ def __init__(self, preprocessors=None):
         elif preprocessors:
             self.preprocessors = (preprocessors,)
 
+    # pylint: disable=R0201
     def fit(self, X, Y, W=None):
         raise RuntimeError(
             "Descendants of Learner must overload method fit or fit_storage")
@@ -106,8 +110,23 @@ def fit_storage(self, data):
         return self.fit(X, Y, W)
 
     def __call__(self, data, progress_callback=None):
-        if not self.check_learner_adequacy(data.domain):
-            raise ValueError(self.learner_adequacy_err_msg)
+
+        for cls in type(self).mro():
+            if 'incompatibility_reason' in cls.__dict__:
+                incompatibility_reason = \
+                    self.incompatibility_reason(data.domain)  # pylint: disable=assignment-from-none
+                if incompatibility_reason is not None:
+                    raise ValueError(incompatibility_reason)
+                break
+            if 'check_learner_adequacy' in cls.__dict__:
+                warnings.warn(
+                    "check_learner_adequacy is deprecated and will be removed "
+                    "in upcoming releases. Learners should instead implement "
+                    "the incompatibility_reason method.",
+                    OrangeDeprecationWarning)
+                if not self.check_learner_adequacy(data.domain):
+                    raise ValueError(self.learner_adequacy_err_msg)
+                break
 
         origdomain = data.domain
 
@@ -176,6 +195,11 @@ def active_preprocessors(self):
     def check_learner_adequacy(self, _):
         return True
 
+    # pylint: disable=no-self-use
+    def incompatibility_reason(self, _: Domain) -> Optional[str]:
+        """Return None if a learner can fit domain or string explaining why it can not."""
+        return None
+
     @property
     def name(self):
         """Return a short name derived from Learner type name"""

Orange/classification/base_classification.py

@@ -5,10 +5,14 @@
 
 
 class LearnerClassification(Learner):
-    learner_adequacy_err_msg = "Categorical class variable expected."
 
-    def check_learner_adequacy(self, domain):
-        return domain.has_discrete_class
+    def incompatibility_reason(self, domain):
+        reason = None
+        if len(domain.class_vars) > 1 and not self.supports_multiclass:
+            reason = "Too many target variables."
+        elif not domain.has_discrete_class:
+            reason = "Categorical class variable expected."
+        return reason
 
 
 class ModelClassification(Model):

Orange/evaluation/clustering.py

@@ -32,6 +32,10 @@ def get_fold(self, fold):
 class ClusteringScore(Score):
     considers_actual = False
 
+    @staticmethod
+    def is_compatible(domain) -> bool:
+        return True
+
     # pylint: disable=arguments-differ
     def from_predicted(self, results, score_function):
         # Clustering scores from labels

Orange/evaluation/scoring.py

@@ -16,7 +16,7 @@
 import sklearn.metrics as skl_metrics
 from sklearn.metrics import confusion_matrix
 
-from Orange.data import DiscreteVariable, ContinuousVariable
+from Orange.data import DiscreteVariable, ContinuousVariable, Domain
 from Orange.misc.wrapper_meta import WrapperMeta
 
 __all__ = ["CA", "Precision", "Recall", "F1", "PrecisionRecallFSupport", "AUC",
@@ -112,14 +112,26 @@ def from_predicted(results, score_function, **kwargs):
              for predicted in results.predicted),
             dtype=np.float64, count=len(results.predicted))
 
+    @staticmethod
+    def is_compatible(domain: Domain) -> bool:
+        raise NotImplementedError
+
 
 class ClassificationScore(Score, abstract=True):
     class_types = (DiscreteVariable, )
 
+    @staticmethod
+    def is_compatible(domain: Domain) -> bool:
+        return domain.has_discrete_class
+
 
 class RegressionScore(Score, abstract=True):
     class_types = (ContinuousVariable, )
 
+    @staticmethod
+    def is_compatible(domain: Domain) -> bool:
+        return domain.has_continuous_class
+
 
 # pylint: disable=invalid-name
 class CA(ClassificationScore):

Orange/evaluation/testing.py

@@ -9,7 +9,7 @@
 
 import sklearn.model_selection as skl
 
-from Orange.data import Table, Domain, ContinuousVariable, DiscreteVariable
+from Orange.data import Domain, ContinuousVariable, DiscreteVariable
 from Orange.data.util import get_unique_names
 
 __all__ = ["Results", "CrossValidation", "LeaveOneOut", "TestOnTrainingData",
@@ -37,9 +37,10 @@ def _mp_worker(fold_i, train_data, test_data, learner_i, learner,
         train_time = time() - t0
         t0 = time()
         # testing
-        if train_data.domain.has_discrete_class:
+        class_var = train_data.domain.class_var
+        if class_var and class_var.is_discrete:
             predicted, probs = model(test_data, model.ValueProbs)
-        elif train_data.domain.has_continuous_class:
+        else:
             predicted = model(test_data, model.Value)
         test_time = time() - t0
     # Different models can fail at any time raising any exception
@@ -269,7 +270,7 @@ def get_augmented_data(self, model_names,
         new_meta_vals = np.empty((len(data), 0))
         names = [var.name for var in chain(domain.attributes,
                                            domain.metas,
-                                           [class_var])]
+                                           domain.class_vars)]
 
         if classification:
             # predictions
@@ -501,8 +502,7 @@ def prepare_arrays(cls, data, indices):
             ptr += len(test)
 
         row_indices = np.concatenate(row_indices, axis=0)
-        actual = data[row_indices].Y.ravel()
-        return folds, row_indices, actual
+        return folds, row_indices, data[row_indices].Y
 
     @staticmethod
     def get_indices(data):
@@ -751,7 +751,7 @@ def __call__(self, data, test_data, learners, preprocessor=None,
             nrows=len(test_data), learners=learners,
             row_indices=np.arange(len(test_data)),
             folds=(Ellipsis, ),
-            actual=test_data.Y.ravel(),
+            actual=test_data.Y,
             score_by_folds=self.score_by_folds,
             train_time=np.zeros((len(learners),)),
             test_time=np.zeros((len(learners),)))

Orange/preprocess/impute.py

@@ -224,7 +224,8 @@ def __call__(self, data, variable):
         variable = data.domain[variable]
         domain = domain_with_class_var(data.domain, variable)
 
-        if self.learner.check_learner_adequacy(domain):
+        incompatibility_reason = self.learner.incompatibility_reason(domain)
+        if incompatibility_reason is None:
             data = data.transform(domain)
             model = self.learner(data)
             assert model.domain.class_var == variable
@@ -239,7 +240,7 @@ def copy(self):
 
     def supports_variable(self, variable):
         domain = Orange.data.Domain([], class_vars=variable)
-        return self.learner.check_learner_adequacy(domain)
+        return self.learner.incompatibility_reason(domain) is None
 
 
 def domain_with_class_var(domain, class_var):

Orange/regression/base_regression.py

@@ -5,10 +5,14 @@
 
 
 class LearnerRegression(Learner):
-    learner_adequacy_err_msg = "Numeric class variable expected."
 
-    def check_learner_adequacy(self, domain):
-        return domain.has_continuous_class
+    def incompatibility_reason(self, domain):
+        reason = None
+        if len(domain.class_vars) > 1 and not self.supports_multiclass:
+            reason = "Too many target variables."
+        elif not domain.has_continuous_class:
+            reason = "Numeric class variable expected."
+        return reason
 
 
 class ModelRegression(Model):

Orange/tests/dummy_learners.py

@@ -33,8 +33,9 @@ def __init__(self, value, prob):
 class DummyMulticlassLearner(SklLearner):
     supports_multiclass = True
 
-    def check_learner_adequacy(self, domain):
-        return all(c.is_discrete for c in domain.class_vars)
+    def incompatibility_reason(self, domain):
+        reason = 'Not all class variables are discrete'
+        return None if all(c.is_discrete for c in domain.class_vars) else reason
 
     def fit(self, X, Y, W):
         rows, class_vars = Y.shape

Orange/tests/test_base.py

@@ -2,28 +2,59 @@
 # pylint: disable=missing-docstring
 import pickle
 import unittest
+from distutils.version import LooseVersion
 
+import Orange
 from Orange.base import SklLearner, Learner, Model
 from Orange.data import Domain, Table
 from Orange.preprocess import Discretize, Randomize, Continuize
 from Orange.regression import LinearRegressionLearner
+from Orange.util import OrangeDeprecationWarning
+
+
+class DummyLearnerDeprecated(Learner):
+
+    def fit(self, *_, **__):
+        return unittest.mock.Mock()
+
+    def check_learner_adequacy(self, _):
+        return True
 
 
 class DummyLearner(Learner):
+
     def fit(self, *_, **__):
         return unittest.mock.Mock()
 
 
 class DummySklLearner(SklLearner):
+
     def fit(self, *_, **__):
         return unittest.mock.Mock()
 
 
 class DummyLearnerPP(Learner):
+
     preprocessors = (Randomize(),)
 
 
 class TestLearner(unittest.TestCase):
+
+    def test_if_deprecation_warning_is_raised(self):
+        with self.assertWarns(OrangeDeprecationWarning):
+            DummyLearnerDeprecated()(Table('iris'))
+
+    def test_check_learner_adequacy_deprecated(self):
+        """This test is to be included in the 3.32 release and will fail in
+        version 3.34. This serves as a reminder to remove the deprecated method
+        and this test."""
+        if LooseVersion(Orange.__version__) >= LooseVersion("3.34"):
+            self.fail(
+                "`Orange.base.Learner.check_learner_adequacy` was deprecated in "
+                "version 3.32, and there have been two minor versions in "
+                "between. Please remove the deprecated method."
+            )
+
     def test_uses_default_preprocessors_unless_custom_pps_specified(self):
         """Learners should use their default preprocessors unless custom
         preprocessors were passed in to the constructor"""