这个问题已经解决了,但…
也考虑Wouter在他原来的评论中提出的解决scheme。 能够处理丢失的数据,包括dropna()
,明确地build立在pandasdropna()
。 除了手动进行性能改进之外,这些function还带有各种可能有用的选项。
In [24]: df = pd.DataFrame(np.random.randn(10,3)) In [25]: df.iloc[::2,0] = np.nan; df.iloc[::4,1] = np.nan; df.iloc[::3,2] = np.nan; In [26]: df Out[26]: 0 1 2 0 NaN NaN NaN 1 2.677677 -1.466923 -0.750366 2 NaN 0.798002 -0.906038 3 0.672201 0.964789 NaN 4 NaN NaN 0.050742 5 -1.250970 0.030561 -2.678622 6 NaN 1.036043 NaN 7 0.049896 -0.308003 0.823295 8 NaN NaN 0.637482 9 -0.310130 0.078891 NaN
In [27]: df.dropna() #drop all rows that have any NaN values Out[27]: 0 1 2 1 2.677677 -1.466923 -0.750366 5 -1.250970 0.030561 -2.678622 7 0.049896 -0.308003 0.823295
In [28]: df.dropna(how='all') #drop only if ALL columns are NaN Out[28]: 0 1 2 1 2.677677 -1.466923 -0.750366 2 NaN 0.798002 -0.906038 3 0.672201 0.964789 NaN 4 NaN NaN 0.050742 5 -1.250970 0.030561 -2.678622 6 NaN 1.036043 NaN 7 0.049896 -0.308003 0.823295 8 NaN NaN 0.637482 9 -0.310130 0.078891 NaN
In [29]: df.dropna(thresh=2) #Drop row if it does not have at least two values that are **not** NaN Out[29]: 0 1 2 1 2.677677 -1.466923 -0.750366 2 NaN 0.798002 -0.906038 3 0.672201 0.964789 NaN 5 -1.250970 0.030561 -2.678622 7 0.049896 -0.308003 0.823295 9 -0.310130 0.078891 NaN
In [30]: df.dropna(subset=[1]) #Drop only if NaN in specific column (as asked in the question) Out[30]: 0 1 2 1 2.677677 -1.466923 -0.750366 2 NaN 0.798002 -0.906038 3 0.672201 0.964789 NaN 5 -1.250970 0.030561 -2.678622 6 NaN 1.036043 NaN 7 0.049896 -0.308003 0.823295 9 -0.310130 0.078891 NaN
还有其他选项(请参阅http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.dropna.html上的文档),其中包括删除列而不是行。
非常方便!