adds silhouettes to output

src/pg/sql/11_kmeans.sql

@@ -18,7 +18,7 @@ CREATE OR REPLACE FUNCTION CDB_KMeansNonspatial(
   id_colname TEXT DEFAULT 'cartodb_id',
   standarize BOOLEAN DEFAULT true
 )
-RETURNS TABLE(cluster_label text, cluster_center json, rowid bigint) AS $$
+RETURNS TABLE(cluster_label text, cluster_center json, silhouettes numeric, rowid bigint) AS $$
 
     from crankshaft.clustering import kmeans_nonspatial
     return kmeans_nonspatial(query, colnames, num_clusters,

src/py/crankshaft/crankshaft/clustering/kmeans.py

@@ -76,11 +76,12 @@ def kmeans_nonspatial(query, colnames, num_clusters=5,
                for c in kmeans.cluster_centers_[kmeans.labels_]]
 
     silhouettes = metrics.silhouette_samples(cluster_columns,
-                                             labels,
+                                             kmeans.labels_,
                                              metric='sqeuclidean')
 
     return zip(kmeans.labels_,
                centers,
+               silhouettes,
                db_resp[0][out_id_colname])