diff --git a/data.py b/data.py
index 6044750490ab965826e7dfa2a7646858bbff4959..24f8222d6b9d9ea5c7f0b232853c7e17a1d6a508 100644
--- a/data.py
+++ b/data.py
@@ -67,6 +67,10 @@ class SKDict(dict):
         keys.update(*(inst.keys() for inst in insts))
         return cls({key: tuple(inst.get(key) for inst in insts) for key in keys})
 
+    @classmethod
+    def concatenate(cls, *insts):
+        return cls.zip(*insts).map(lambda x: np.concatenate(x))
+
     def only(self, *keys):
         return self.__class__({key: self[key] for key in keys})