Add ability to add DensityEstimator as a Clusterer

yellowbrick/cluster/base.py

@@ -17,7 +17,7 @@
 ## Imports
 ##########################################################################
 
-from yellowbrick.utils import isclusterer
+from yellowbrick.utils import isclusterer, isdensity
 from yellowbrick.base import ScoreVisualizer
 from yellowbrick.exceptions import YellowbrickTypeError
 
@@ -41,7 +41,7 @@ class ClusteringScoreVisualizer(ScoreVisualizer):
     """
 
     def __init__(self, estimator, ax=None, fig=None, force_model=False, **kwargs):
-        if not force_model and not isclusterer(estimator):
+        if not force_model and not isclusterer(estimator) and not isdensity(estimator):
             raise YellowbrickTypeError(
                 "The supplied model is not a clustering estimator; try a "
                 "classifier or regression score visualizer instead!"

yellowbrick/cluster/silhouette.py

@@ -188,7 +188,7 @@ def fit(self, X, y=None, **kwargs):
         # Compute the number of available clusters from the estimator
         if hasattr(self.estimator, "n_clusters"):
             self.n_clusters_ = self.estimator.n_clusters
-        else:
+	else:
             unique_labels = set(labels)
             n_noise_clusters = 1 if -1 in unique_labels else 0
             self.n_clusters_ = len(unique_labels) - n_noise_clusters

yellowbrick/utils/types.py

@@ -116,6 +116,25 @@ def is_clusterer(estimator):
 isclusterer = is_clusterer
 
 
+def is_density(estimator):
+    """
+    Returns True if the given estimator is a Density Estimator.
+
+    Parameters
+    ----------
+    estimator : class or instance
+        The object to test if it is a Scikit-Learn clusterer, especially a
+        Scikit-Learn estimator or Yellowbrick visualizer
+    """
+
+    # Test the _estimator_type property
+    return getattr(estimator, "_estimator_type", None) == "DensityEstimator"
+
+
+# Alias for closer name to isinstance and issubclass
+isdensity = is_density
+
+
 def is_gridsearch(estimator):
     """
     Returns True if the given estimator is a clusterer.