i有2个数据范围DF1和DF2,具有相同的列名['a',''b','c'],并由日期索引。日期索引可以具有相似的值。我想创建一个仅使用列['c']的数据分别重命名的'df1'和'df2'和正确的日期索引的dataframe df3。我的问题是我无法正确合并索引。
df1 = pd.DataFrame(np.random.randn(5,3), index=pd.date_range('01/02/2014',periods=5,freq='D'), columns=['a','b','c'] )
df2 = pd.DataFrame(np.random.randn(8,3), index=pd.date_range('01/01/2014',periods=8,freq='D'), columns=['a','b','c'] )
df1
a b c
2014-01-02 0.580550 0.480814 1.135899
2014-01-03 -1.961033 0.546013 1.093204
2014-01-04 2.063441 -0.627297 2.035373
2014-01-05 0.319570 0.058588 0.350060
2014-01-06 1.318068 -0.802209 -0.939962
df2
a b c
2014-01-01 0.772482 0.899337 0.808630
2014-01-02 0.518431 -1.582113 0.323425
2014-01-03 0.112109 1.056705 -1.355067
2014-01-04 0.767257 -2.311014 0.340701
2014-01-05 0.794281 -1.954858 0.200922
2014-01-06 0.156088 0.718658 -1.030077
2014-01-07 1.621059 0.106656 -0.472080
2014-01-08 -2.061138 -2.023157 0.257151
DF3数据框应具有以下形式:
df3
df1 df2
2014-01-01 NaN 0.808630
2014-01-02 1.135899 0.323425
2014-01-03 1.093204 -1.355067
2014-01-04 2.035373 0.340701
2014-01-05 0.350060 0.200922
2014-01-06 -0.939962 -1.030077
2014-01-07 NaN -0.472080
2014-01-08 NaN 0.257151
但是,由于DF1列中的NAN作为DF2的日期索引更宽。(在此示例中,我将获得NAN的wollow日期:2014-01-01, 2014-01-07 and 2014-01-08
)
感谢您的帮助。
您可以使用concat:
In [11]: pd.concat([df1['c'], df2['c']], axis=1, keys=['df1', 'df2'])
Out[11]:
df1 df2
2014-01-01 NaN -0.978535
2014-01-02 -0.106510 -0.519239
2014-01-03 -0.846100 -0.313153
2014-01-04 -0.014253 -1.040702
2014-01-05 0.315156 -0.329967
2014-01-06 -0.510577 -0.940901
2014-01-07 NaN -0.024608
2014-01-08 NaN -1.791899
[8 rows x 2 columns]
轴参数确定数据框的堆叠方式:
df1 = pd.DataFrame([1, 2, 3])
df2 = pd.DataFrame(['a', 'b', 'c'])
pd.concat([df1, df2], axis=0)
0
0 1
1 2
2 3
0 a
1 b
2 c
pd.concat([df1, df2], axis=1)
0 0
0 1 a
1 2 b
2 3 c
好吧,我不确定合并是否是必经之路。我个人将通过创建日期索引,然后使用列表综合构建列来构建新的数据框架。可能不是最Pythonic的方式,但似乎对我有用!
import pandas as pd
import numpy as np
df1 = pd.DataFrame(np.random.randn(5,3), index=pd.date_range('01/02/2014',periods=5,freq='D'), columns=['a','b','c'] )
df2 = pd.DataFrame(np.random.randn(8,3), index=pd.date_range('01/01/2014',periods=8,freq='D'), columns=['a','b','c'] )
# Create an index list from the set of dates in both data frames
Index = list(set(list(df1.index) + list(df2.index)))
Index.sort()
df3 = pd.DataFrame({'df1': [df1.loc[Date, 'c'] if Date in df1.index else np.nan for Date in Index],
'df2': [df2.loc[Date, 'c'] if Date in df2.index else np.nan for Date in Index],},
index = Index)
df3
您要求的是加入操作。使用how
参数,您可以定义如何处理唯一的索引。在这里,一些文章在这一点上看起来很有帮助。在下面的示例中,我省略了化妆品(例如重命名列),以简单。
代码
import numpy as np
import pandas as pd
df1 = pd.DataFrame(np.random.randn(5,3), index=pd.date_range('01/02/2014',periods=5,freq='D'), columns=['a','b','c'] )
df2 = pd.DataFrame(np.random.randn(8,3), index=pd.date_range('01/01/2014',periods=8,freq='D'), columns=['a','b','c'] )
df3 = df1.join(df2, how='outer', lsuffix='_df1', rsuffix='_df2')
print(df3)
输出
a_df1 b_df1 c_df1 a_df2 b_df2 c_df2
2014-01-01 NaN NaN NaN 0.109898 1.107033 -1.045376
2014-01-02 0.573754 0.169476 -0.580504 -0.664921 -0.364891 -1.215334
2014-01-03 -0.766361 -0.739894 -1.096252 0.962381 -0.860382 -0.703269
2014-01-04 0.083959 -0.123795 -1.405974 1.825832 -0.580343 0.923202
2014-01-05 1.019080 -0.086650 0.126950 -0.021402 -1.686640 0.870779
2014-01-06 -1.036227 -1.103963 -0.821523 -0.943848 -0.905348 0.430739
2014-01-07 NaN NaN NaN 0.312005 0.586585 1.531492
2014-01-08 NaN NaN NaN -0.077951 -1.189960 0.995123