Changed use of Dataset.get_matrix() to Dataset.asarray() and removed it.

system/dataset.py

@@ -160,10 +160,6 @@ class Dataset:
         """Returns dataset name"""
         return self._name
 
-    def get_matrix(self):
-        """Returns internal numeric matrix for dataset."""
-        return self._array
-
     def get_all_dims(self):
         """Returns all dimensions in project"""
         return self._all_dims