[英]Assigning a 2d array of values to a Pandas multiindex dataframe
I have outputs from calculations that is best stored in a Pandas MultiIndex format. 我的计算结果最好以Pandas MultiIndex格式存储。 For concrete purposes, let us consider the form below (though the actual structure is dictated programmatically)
出于具体目的,让我们考虑以下形式(尽管实际结构是通过编程确定的)
X Y Z
DATE
2018-01-01 A NaN NaN NaN
B NaN NaN NaN
C NaN NaN NaN
2018-01-02 A NaN NaN NaN
B NaN NaN NaN
C NaN NaN NaN
I want to assign the numpy array outputs to a particular time slice. 我想将numpy数组输出分配给特定的时间片。 Say I have
说我有
output = np.array([[1,2,3],[2,2,1],[4,2,3]])
so the desired output is 所以所需的输出是
X Y Z
DATE
2018-01-01 A NaN NaN NaN
B NaN NaN NaN
C NaN NaN NaN
2018-01-02 A 1 2 3
B 2 2 1
C 4 2 3
I have tried pandas.IndexSlice where j is the j-th time slice. 我尝试了pandas.IndexSlice,其中j是第j个时间片。
df.loc[pd.IndexSlice[j,:], :] = output
but that doesn't work. 但这不起作用。 I have also tried by replacing loc by iloc but to no avail.
我也尝试过用loc代替loc,但无济于事。 In non-MultiIndex dataframes, I can assign a list to a particular column in a DataFrame without having to assign each element individually.
在非MultiIndex数据框中,我可以将列表分配给DataFrame中的特定列,而不必分别分配每个元素。 Is there a way to do it for a matrix into a MultiIndex dataframe?
有没有一种方法可以将矩阵转换为MultiIndex数据帧?
your code works just fine. 您的代码工作正常。
Demo: 演示:
In [70]: df.loc[pd.IndexSlice['2018-01-02', :], :] = output
In [71]: df
Out[71]:
X Y Z
DATE I2
2018-01-01 A NaN NaN NaN
B NaN NaN NaN
C NaN NaN NaN
2018-01-02 A 1.0 2.0 3.0
B 2.0 2.0 1.0
C 4.0 2.0 3.0
PS i tested both options when the DATE
index column is of string
and when it's is of datetime
dtype - in both cases the code above is working properly. PS i在
DATE
索引列为string
且datetime
dtype时测试了这两个选项-在上述两种情况下,以上代码均能正常工作。
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