以日期爲索引合併大熊貓數據框

我試圖合併兩個不同長度的數據框（稱爲df1和df2），這兩個數據框都是通過日期索引的。 dfs（df1）中較長的一個列出了所有日期中較短的一個（df2）。我嘗試使用以下命令將它們合併：merged = df2.merge(df1, on='Date')，但是當我嘗試這樣做時，出現以下錯誤，我不明白。以日期爲索引合併大熊貓數據框

--------------------------------------------------------------------------- 
KeyError         Traceback (most recent call last) 
<ipython-input-47-e8d3e1ec920d> in <module>() 
----> 1 merged = df2.merge(df1, on='Date') 

/usr/lib/python2.7/dist-packages/pandas/core/frame.pyc in merge(self, right, how, on, left_on, right_on, left_index, right_index, sort, suffixes, copy) 
    3630      left_on=left_on, right_on=right_on, 
    3631      left_index=left_index, right_index=right_index, sort=sort, 
-> 3632      suffixes=suffixes, copy=copy) 
    3633 
    3634  #---------------------------------------------------------------------- 

/usr/lib/python2.7/dist-packages/pandas/tools/merge.pyc in merge(left, right, how, on, left_on, right_on, left_index, right_index, sort, suffixes, copy) 
    37       right_on=right_on, left_index=left_index, 
    38       right_index=right_index, sort=sort, suffixes=suffixes, 
---> 39       copy=copy) 
    40  return op.get_result() 
    41 if __debug__: 

/usr/lib/python2.7/dist-packages/pandas/tools/merge.pyc in __init__(self, left, right, how, on, left_on, right_on, axis, left_index, right_index, sort, suffixes, copy) 
    181   (self.left_join_keys, 
    182   self.right_join_keys, 
--> 183   self.join_names) = self._get_merge_keys() 
    184 
    185  def get_result(self): 

/usr/lib/python2.7/dist-packages/pandas/tools/merge.pyc in _get_merge_keys(self) 
    324     else: 
    325      if not is_rkey(rk): 
--> 326       right_keys.append(right[rk].values) 
    327       if lk == rk: 
    328        # avoid key upcast in corner case (length-0) 

/usr/lib/python2.7/dist-packages/pandas/core/frame.pyc in __getitem__(self, key) 
    1656    return self._getitem_multilevel(key) 
    1657   else: 
-> 1658    return self._getitem_column(key) 
    1659 
    1660  def _getitem_column(self, key): 

/usr/lib/python2.7/dist-packages/pandas/core/frame.pyc in _getitem_column(self, key) 
    1663   # get column 
    1664   if self.columns.is_unique: 
-> 1665    return self._get_item_cache(key) 
    1666 
    1667   # duplicate columns & possible reduce dimensionaility 

/usr/lib/python2.7/dist-packages/pandas/core/generic.pyc in _get_item_cache(self, item) 
    1003   res = cache.get(item) 
    1004   if res is None: 
-> 1005    values = self._data.get(item) 
    1006    res = self._box_item_values(item, values) 
    1007    cache[item] = res 

/usr/lib/python2.7/dist-packages/pandas/core/internals.pyc in get(self, item) 
    2872     return self.get_for_nan_indexer(indexer) 
    2873 
-> 2874    _, block = self._find_block(item) 
    2875    return block.get(item) 
    2876   else: 

/usr/lib/python2.7/dist-packages/pandas/core/internals.pyc in _find_block(self, item) 
    3184 
    3185  def _find_block(self, item): 
-> 3186   self._check_have(item) 
    3187   for i, block in enumerate(self.blocks): 
    3188    if item in block: 

/usr/lib/python2.7/dist-packages/pandas/core/internals.pyc in _check_have(self, item) 
    3191  def _check_have(self, item): 
    3192   if item not in self.items: 
-> 3193    raise KeyError('no item named %s' % com.pprint_thing(item)) 
    3194 
    3195  def reindex_axis(self, new_axis, indexer=None, method=None, axis=0, 

KeyError: u'no item named Date'

我也試着落下on='Date'因爲二者都是已經被收錄日期，但結果似乎是相同的。任何想法，我可能會出錯哪裏？

來源

2014-04-24 neanderslob

使用'join'而不是'merge';它默認會在索引上合併。 –

@KarlD。感謝您的迴應！所以，如果我理解正確，它應該是這樣的：'merged = df2.join（df1）'？ – neanderslob

@KarlD。我試了一下，得到了[這些錯誤]（https://dl.dropboxusercontent.com/u/11993667/joined）。不幸的是，我不知道他們的意思。 – neanderslob

我認爲這是最自然的使用join，因爲它默認情況下合併索引。因此，像下面：

merged = df2.join(df1,rsuffix='_y')

添加rsuffix='_y'，因爲你必須在這兩個dataframes公共列名。

來源

2014-04-25 06:51:30

以日期爲索引合併大熊貓數據框

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