0

使用 a DataFrame，您可以Series在使用DataFrame.apply生成DataFrame带有新列的新列时输出

          a         b         c
0 -0.119342  0.286710  0.266750
1 -1.514301  0.556106 -2.743888
2 -0.156469 -0.352915 -1.963398
3  1.165479  1.364303  0.648178
4  1.541738  0.714239 -1.468896

def f(x):
    return pandas.Series([ x['a']+x['b'], x['b'] + x['c'], x['a'] + x['c'] ], index=['ab', 'bc', 'ac'])

In [52]: df.apply(f, axis=1)
Out[52]: 
         ab        bc        ac
0  0.167368  0.553460  0.147408
1 -0.958195 -2.187782 -4.258188
2 -0.509384 -2.316313 -2.119867
3  2.529782  2.012481  1.813658
4  2.255977 -0.754657  0.072842

尝试输出新DataFrame对象而不是Series对象会导致堆叠对象而不是创建内聚DataFrame

In [53]: def f(x):
    return pandas.DataFrame([[ x['a']+x['b'], x['b'] + x['c'], x['a'] + x['c'] ]], columns=['ab', 'bc', 'ac'])
   ....: 

In [54]: df.apply(f, axis=1)
Exception ValueError: ValueError('Cannot call bool() on DataFrame.',) in 'util._checknull' ignored
Exception ValueError: ValueError('Cannot call bool() on DataFrame.',) in 'util._checknull' ignored
Exception ValueError: ValueError('Cannot call bool() on DataFrame.',) in 'util._checknull' ignored
Exception ValueError: ValueError('Cannot call bool() on DataFrame.',) in 'util._checknull' ignored
Exception ValueError: ValueError('Cannot call bool() on DataFrame.',) in 'util._checknull' ignored
Exception ValueError: ValueError('Cannot call bool() on DataFrame.',) in 'util._checknull' ignored
Exception ValueError: ValueError('Cannot call bool() on DataFrame.',) in 'util._checknull' ignored
Exception ValueError: ValueError('Cannot call bool() on DataFrame.',) in 'util._checknull' ignored
Exception ValueError: ValueError('Cannot call bool() on DataFrame.',) in 'util._checknull' ignored
Exception ValueError: ValueError('Cannot call bool() on DataFrame.',) in 'util._checknull' ignored
Out[54]: 
0             ab       bc        ac
0  0.167368  0.553
1             ab        bc        ac
0 -0.958195 -2.18
2             ab        bc        ac
0 -0.509384 -2.31
3             ab        bc        ac
0  2.529782  2.01
4             ab        bc        ac
0  2.255977 -0.75

有没有办法输出DataFrames （或多个Series），可以像输出单个Series对象一样堆叠？

4

1 回答 1

1

除了repr中的警告（我为此创建了一个问题：https ://github.com/pydata/pandas/issues/1749 ）之外，您尝试做的似乎工作正常

In [57]: df
Out[57]:
          a         b         c
0 -0.119342  0.286710  0.266750
1 -1.514301  0.556106 -2.743888
2 -0.156469 -0.352915 -1.963398
3  1.165479  1.364303  0.648178
4  1.541738  0.714239 -1.468896

In [58]: s = df.apply(f, axis=1)

In [59]: type(s)
Out[59]: pandas.core.series.Series

In [60]: type(s[0])
Out[60]: pandas.core.frame.DataFrame

In [61]: s[0]
Out[61]:
         ab       bc        ac
0  0.167368  0.55346  0.147408

In [62]: s
Exception ValueError: ValueError('Cannot call bool() on DataFrame.',) in 'util._checknull' ignored
Exception ValueError: ValueError('Cannot call bool() on DataFrame.',) in 'util._checknull' ignored
Exception ValueError: ValueError('Cannot call bool() on DataFrame.',) in 'util._checknull' ignored
Exception ValueError: ValueError('Cannot call bool() on DataFrame.',) in 'util._checknull' ignored
Exception ValueError: ValueError('Cannot call bool() on DataFrame.',) in 'util._checknull' ignored
Exception ValueError: ValueError('Cannot call bool() on DataFrame.',) in 'util._checknull' ignored
Exception ValueError: ValueError('Cannot call bool() on DataFrame.',) in 'util._checknull' ignored
Exception ValueError: ValueError('Cannot call bool() on DataFrame.',) in 'util._checknull' ignored
Exception ValueError: ValueError('Cannot call bool() on DataFrame.',) in 'util._checknull' ignored
Exception ValueError: ValueError('Cannot call bool() on DataFrame.',) in 'util._checknull' ignored
Out[62]:
0             ab       bc        ac
0  0.167368  0.553
1             ab        bc        ac
0 -0.958195 -2.18
2             ab        bc        ac
0 -0.509384 -2.31
3             ab        bc        ac
0  2.529782  2.01
4             ab        bc        ac
0  2.255977 -0.75
于 2012-08-09T12:51:28.660 回答