Better error message per issue #220

Author: lmcinnes

hdbscan/hdbscan_.py

@@ -503,6 +503,9 @@ def hdbscan(X, min_cluster_size=5, min_samples=None, alpha=1.0,
         min_samples = 1
 
     if algorithm != 'best':
+        if metric != 'precomputed' and issparse(X) and metric != 'generic':
+            raise ValueError("Sparse data matrices only support algorithm 'generic'.")
+                  
         if algorithm == 'generic':
             (single_linkage_tree,
              result_min_span_tree) = memory.cache(