DOC Broken link in optics_.py

Author: qinhanmin2014

sklearn/cluster/optics_.py

@@ -59,7 +59,7 @@ def optics(X, min_samples=5, max_bound=np.inf, metric='euclidean',
 
     p : integer, optional (default=2)
         Parameter for the Minkowski metric from
-        :ref:`sklearn.metrics.pairwise_distances`. When p = 1, this is
+        :class:`sklearn.metrics.pairwise_distances`. When p = 1, this is
         equivalent to using manhattan_distance (l1), and euclidean_distance
         (l2) for p = 2. For arbitrary p, minkowski_distance (l_p) is used.
 
@@ -173,7 +173,7 @@ class OPTICS(BaseEstimator, ClusterMixin):
 
     p : integer, optional (default=2)
         Parameter for the Minkowski metric from
-        :ref:`sklearn.metrics.pairwise_distances`. When p = 1, this is
+        :class:`sklearn.metrics.pairwise_distances`. When p = 1, this is
         equivalent to using manhattan_distance (l1), and euclidean_distance
         (l2) for p = 2. For arbitrary p, minkowski_distance (l_p) is used.