我有一个混合的 pd.DataFrame:
import pandas as pd import numpy as np df = pd.DataFrame({ 'A' : 1., 'B' : pd.Timestamp('20130102'), 'C' : pd.Timestamp('20180101'), 'D' : np.random.rand(10), 'F' : 'foo' }) df Out[12]: A B C D F 0 1.0 2013-01-02 2018-01-01 0.592533 foo 1 1.0 2013-01-02 2018-01-01 0.819248 foo 2 1.0 2013-01-02 2018-01-01 0.298035 foo 3 1.0 2013-01-02 2018-01-01 0.330128 foo 4 1.0 2013-01-02 2018-01-01 0.371705 foo 5 1.0 2013-01-02 2018-01-01 0.541246 foo 6 1.0 2013-01-02 2018-01-01 0.976108 foo 7 1.0 2013-01-02 2018-01-01 0.423069 foo 8 1.0 2013-01-02 2018-01-01 0.863764 foo 9 1.0 2013-01-02 2018-01-01 0.037085 foo我想聚合我的数字列,但也要保留非数字列.如果我执行 gropuby 后跟 agg.我得到:
I would like to aggregate my numerical columns, but keep also the non-numerical ones. If I do a gropuby followed by agg. I get:
df.groupby('B').agg(np.median) Out[13]: A D B 2013-01-02 1.0 0.482157这很好,我知道这是期望的行为,因为其他 dtypes 可能会在 np.median 期间引发异常,但我也想获得我的原始列 F 值 foo,以及 C 和 2018-01-01
which is fine, and I know is desired behavior as the other dtypes probably raise exceptions during np.median, but I would like to get also my original column F with value foo, as well as C with 2018-01-01
到目前为止,我已经用自定义包装器解决了我的数值聚合函数,例如如果我想对我的数据框执行 nanmean:
So far, I have solved with a custom wrapper to my numerical aggregation functions e.g. if I wanted to do a nanmean over my dataframe:
def my_nan_median(x): if isinstance(x.values[0], np.datetime64): return np.min(x) # let the first datetime pass! elif isinstance(x.values[0], str): return x.values[0] # let the strings pass! else: return np.nanmedian(x)但它看起来很糟糕.这样做的正确方法是什么?
but it looks awful. What is the right way to do so?
推荐答案通过使用 select_dtypes:
df.groupby(list(df.select_dtypes(exclude=[np.number]))).agg(np.median).reset_index()或者像这样:
df1 = df.groupby('B',as_index=False).agg(np.median) pd.concat([df1,df.drop_duplicates(['B']).drop(list(df1),1).reset_index(drop=True)],axis=1)更多推荐
如何仅聚合混合 dtypes 数据框中的数字列
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