DOC: document ignore_index in concat in docstring and sphinx docs, GH #619

Author: wesm

doc/source/merging.rst

@@ -72,6 +72,10 @@ some configurable handling of "what to do with the other axes":
 - ``verify_integrity``: boolean, default False. Check whether the new
   concatenated axis contains duplicates. This can be very expensive relative
   to the actual data concatenation
+- ``ignore_index`` : boolean, default False. If True, do not use the index
+  values on the concatenation axis. The resulting axis will be labeled 0, ...,
+  n - 1. This is useful if you are concatenating objects where the
+  concatenation axis does not have meaningful indexing information.
 
 Without a little bit of context and example many of these arguments don't make
 much sense. Let's take the above example. Suppose we wanted to associate

pandas/tools/merge.py

@@ -622,6 +622,11 @@ def concat(objs, axis=0, join='outer', join_axes=None, ignore_index=False,
         MultiIndex. Otherwise they will be inferred from the keys
     names : list, default None
         Names for the levels in the resulting hierarchical index
+    ignore_index : boolean, default False
+        If True, do not use the index values on the concatenation axis. The
+        resulting axis will be labeled 0, ..., n - 1. This is useful if you are
+        concatenating objects where the concatenation axis does not have
+        meaningful indexing information.
 
     Notes
     -----