added copy

system/dataset.py

@@ -1,4 +1,4 @@
-from scipy import ndarray,atleast_2d,asarray
+from scipy import ndarray,atleast_2d,asarray,intersect1d
 from scipy import sort as array_sort
 from itertools import izip
 import shelve
@@ -156,13 +156,13 @@ class Dataset:
         given dim.  Index (Indices) are the Identifiers position in a
         matrix in a given dim.
         """
-        try:
+        if indices!=None:
             if len(indices)==0:# if empty list or empty array
-                indices=[]
-        except:
-            pass
+                return []
         
         if indices != None:
+            # be sure to match intersection
+            #indices = intersect1d(self.get_indices(dim),indices)
             ids = [self._map[dim].reverse[i] for i in indices]
 	else:
             if sorted==True:
@@ -174,7 +174,6 @@ class Dataset:
         
     def get_indices(self, dim, idents=None):
         """Returns indices for identifiers along dimension.
-
         You can optionally provide a list of identifiers to retrieve a
         index subset.
         
@@ -192,6 +191,8 @@ class Dataset:
         return asarray(index)        
 
     def copy(self):
+        """ Returns deepcopy of dataset.
+        """
         return copy.deepcopy(self)