Change to allow grouping order to be preserved

Author: adkinsrs

diffxpy/testing/utils.py

@@ -111,7 +111,8 @@ def parse_grouping(data, sample_description, grouping):
 
 def split_x(data, grouping):
     grouping = np.asarray(grouping)
-    groups = np.unique(grouping)
+    #groups = np.unique(grouping)
+    groups = pd.Series(grouping).unique()
     x0 = data[np.where(grouping == groups[0])[0]]
     x1 = data[np.where(grouping == groups[1])[0]]
     return x0, x1