pass in right type to [o] Par - PDLPorters/pdl#511

Cluster.pd

@@ -714,6 +714,14 @@ pp_def
   Doc => ('K-Means clustering algorithm. The "ctrMethodFlag" determines how
 clusters centroids are to be computed; see getclustercentroids() for details.
 
+Because the C library code reads from the C<clusterids> if and only if
+C<npass> is 0, before writing to it, it would be inconvenient to
+set it to C<[io]>. However for efficiency reasons, as of 2.096, PDL
+will not convert it (force a read-back on the conversion) for you
+if you pass in the wrongly-typed data. This means that you should
+be careful to pass in C<long> data of the right size if you set C<npass>
+to 0.
+
 See also: kmedoids().
 '),
 );

t/030_kcluster.t

@@ -142,7 +142,7 @@ PDL::Cluster::kcluster(
 		       $mask2,
 		       $weight2,
 		       0,
-		       ($clusters=$initialid->copy),
+		       ($clusters=$initialid->long),
 		       ($error=null),
 		       ($nfound=null),
 		       $params{dist},