Updated documentation for mode()

Improved after review. Backtick for code mode, new paragraph for the note, iloc instead of ix for integer indices.

Author: alfonsomhc

pandas/core/frame.py

@@ -4413,11 +4413,12 @@ def mode(self, axis=0, numeric_only=False):
         """
         Gets the mode(s) of each element along the axis selected. Empty if nothing
         has 2+ occurrences. Adds a row for each mode per label, fills in gaps
-        with nan. Note that there could be multiple values returned for the selected
+        with nan. 
+        Note that there could be multiple values returned for the selected
         axis (when more than one item share the maximum frequency), which is the 
-        reason why a dataframe is returned. This means that if you want to impute 
-        missing values with the mode in a dataframe df, you can just do this: 
-        df.fillna(df.mode().ix[0])
+        reason why a dataframe is returned. If you want to impute missing values 
+        with the mode in a dataframe ``df``, you can just do this: 
+        ``df.fillna(df.mode().iloc[0])``
 
         Parameters
         ----------