from previous page) 1 b 2 c 3 aaba 4 baca 5 NaN 6 caba 7 dog 8 cat dtype: object 3.2.6 Merge Concat pandas provides various facilities for easily combining together Series and DataFrame objects various kinds of set logic for the indexes and relational algebra functionality in the case of join / merge-type operations. See the Merging section. Concatenating pandas objects together with concat(): Out[79]: key lval 0 foo 1 1 foo 2 In [80]: right Out[80]: key rval 0 foo 4 1 foo 5 In [81]: pd.merge(left, right, on='key') Out[81]: key lval rval 0 foo 1 4 1 foo 1 5 2 foo 2 4 3 foo 2 5 Another example

features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 11 Merge, join, and concatenate 129 11.1 Concatenating objects . . . . . . . . . . . . . . . . . . . . . axis=1 to obtain a DataFrame (#787) 1.2 v.0.7.0 (February 9, 2012) 1.2.1 New features • New unified merge function for efficiently performing full gamut of database / relational-algebra operations. Refactored was an implementation headache). 128 Chapter 10. Group By: split-apply-combine CHAPTER ELEVEN MERGE, JOIN, AND CONCATENATE pandas provides various facilities for easily combining together Series, DataFrame

features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 11 Merge, join, and concatenate 129 11.1 Concatenating objects . . . . . . . . . . . . . . . . . . . . . to obtain a DataFrame (GH787) 1.3 v.0.7.0 (February 9, 2012) 1.3.1 New features • New unified merge function for efficiently performing full gamut of database / relational-algebra operations. Refactored was an implementation headache). 128 Chapter 10. Group By: split-apply-combine CHAPTER ELEVEN MERGE, JOIN, AND CONCATENATE pandas provides various facilities for easily combining together Series, DataFrame

features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 11 Merge, join, and concatenate 137 11.1 Concatenating objects . . . . . . . . . . . . . . . . . . . . . analysis toolkit, Release 0.7.3 1.4 v.0.7.0 (February 9, 2012) 1.4.1 New features • New unified merge function for efficiently performing full gamut of database / relational-algebra operations. Refactored was an implementation headache). 136 Chapter 10. Group By: split-apply-combine CHAPTER ELEVEN MERGE, JOIN, AND CONCATENATE pandas provides various facilities for easily combining together Series, DataFrame

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159 2.1.6 Merge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 2 Miscellaneous indexing FAQ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 501 2.7 Merge, join, concatenate and compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1006 2.27.7 Merge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1006

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159 2.1.6 Merge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 2 Miscellaneous indexing FAQ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 501 2.7 Merge, join, concatenate and compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1005 2.27.7 Merge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1005

• Bug in Categorical.astype() not allowing for casting to extension dtypes (GH28668) • Bug where merge() was unable to join on categorical and extension dtype columns (GH28668) • Categorical.searchsorted() when margins=True and aggfunc='mean' (GH24893) • Bug merge_asof() could not use datetime.timedelta for tolerance kwarg (GH28098) • Bug in merge(), did not append suffixes correctly with MultiIndex (GH28518) qcut() and cut() now handle boolean input (GH20303) • Fix to ensure all int dtypes can be used in merge_asof() when using a tolerance value. Previously every non-int64 type would raise an erroneous MergeError

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 2.1.6 Merge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 2 Miscellaneous indexing FAQ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 478 2.7 Merge, join, concatenate and compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 963 2.27.7 Merge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 964 2

features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 1.8.1.1 merge_asof for asof-style time-series joining . . . . . . . . . . . . . . . . . . . 82 1.8.1.2 .rolling() Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438 5.6 Merge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Resampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477 7.7 Merge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

column names with backticks to refer to names with spaces (GH6508) • merge_asof() now gives a more clear error message when merge keys are categoricals that are not equal (GH26136) • pandas.core.window 1.6.15 Reshaping • Bug in pandas.merge() adds a string of None, if None is assigned in suffixes instead of remain the column name as-is (GH24782). • Bug in merge() when merging by index name would sometimes where the resulting freq of two DatetimeIndex with the same freq would be dropped (GH3232). • Bug in merge() where merging with equivalent Categorical dtypes was raising an error (GH22501) • bug in DataFrame