diff --git a/src/clj_ml/utils.clj b/src/clj_ml/utils.clj
index 76cabdb..a580e3d 100644
--- a/src/clj_ml/utils.clj
+++ b/src/clj_ml/utils.clj
@@ -29,6 +29,12 @@
       (.addElement fv item))
     fv))
 
+(defn map-fast-vec [^weka.core.FastVector fast-vector f]
+  (->> (.elements fast-vector)
+       enumeration-seq
+       (map f)
+       into-fast-vector))
+
 (defn update-in-when
   "Similar to update-in, but returns m unmodified if any levels do
   not exist"