Python Pandas Multindex专栏 [英] Python pandas Multindex column
问题描述
首先,我在jupyter笔记本中使用python 3.50.
First of all, I'm using python 3.50 in a jupyter notebook.
我想创建一个DataFrame以在报表中显示一些数据.我希望它具有两个索引列(如果要引用的术语不正确,请问问.我不习惯与熊猫一起工作).
I want to create a DataFrame for showing some data in a report. I want it to have two index column (Excuse me if the term to refer it is not the correct. I'm not use to work with pandas).
我有可以运行的示例代码:
I have this example code that works:
frame = pd.DataFrame(np.arange(12).reshape(( 4, 3)),
index =[['a', 'a', 'b', 'b'], [1, 2, 1, 2]],
columns =[['Ohio', 'Ohio', 'Ohio'], ['Green', 'Red', 'Green']])
但是当我尝试解决这个问题时,它给了我一个错误:
But when I try to take it to my case, it gives me an error:
cell_rise_Inv= pd.DataFrame([[0.00483211, 0.00511619, 0.00891821, 0.0449637, 0.205753],
[0.00520049, 0.00561577, 0.010993, 0.0468998, 0.207461],
[0.00357213, 0.00429087, 0.0132186, 0.0536389, 0.21384],
[-0.0021868, -0.0011312, 0.0120546, 0.0647213, 0.224749],
[-0.0725403, -0.0700884, -0.0382486, 0.0899121, 0.313639]],
index =[['transition [ns]','transition [ns]','transition [ns]','transition [ns]','transition [ns]'],
[0.0005, 0.001, 0.01, 0.1, 0.5]],
columns =[[0.01, 0.02, 0.05, 0.1, 0.5],['capacitance [pF]','capacitance [pF]','capacitance [pF]','capacitance [pF]','capacitance [pF]']])
cell_rise_Inv
---------------------------------------------------------------------------
AssertionError Traceback (most recent call last)
<ipython-input-89-180a1ad88403> in <module>()
6 index =[['transition [ns]','transition [ns]','transition [ns]','transition [ns]','transition [ns]'],
7 [0.0005, 0.001, 0.01, 0.1, 0.5]],
----> 8 columns =[[0.01, 0.02, 0.05, 0.1, 0.5],['capacitance [pF]','capacitance [pF]','capacitance [pF]','capacitance [pF]','capacitance [pF]']])
9 cell_rise_Inv
C:\Users\Josele\Anaconda3\lib\site-packages\pandas\core\frame.py in __init__(self, data, index, columns, dtype, copy)
261 if com.is_named_tuple(data[0]) and columns is None:
262 columns = data[0]._fields
--> 263 arrays, columns = _to_arrays(data, columns, dtype=dtype)
264 columns = _ensure_index(columns)
265
C:\Users\Josele\Anaconda3\lib\site-packages\pandas\core\frame.py in _to_arrays(data, columns, coerce_float, dtype)
5350 if isinstance(data[0], (list, tuple)):
5351 return _list_to_arrays(data, columns, coerce_float=coerce_float,
-> 5352 dtype=dtype)
5353 elif isinstance(data[0], collections.Mapping):
5354 return _list_of_dict_to_arrays(data, columns,
C:\Users\Josele\Anaconda3\lib\site-packages\pandas\core\frame.py in _list_to_arrays(data, columns, coerce_float, dtype)
5429 content = list(lib.to_object_array(data).T)
5430 return _convert_object_array(content, columns, dtype=dtype,
-> 5431 coerce_float=coerce_float)
5432
5433
C:\Users\Josele\Anaconda3\lib\site-packages\pandas\core\frame.py in _convert_object_array(content, columns, coerce_float, dtype)
5487 # caller's responsibility to check for this...
5488 raise AssertionError('%d columns passed, passed data had %s '
-> 5489 'columns' % (len(columns), len(content)))
5490
5491 # provide soft conversion of object dtypes
AssertionError: 2 columns passed, passed data had 5 columns
有什么想法吗?我不明白为什么该示例起作用,而我的示例却不这样做. :S
Any ideas? I can't understand why the example works and mine don't do it. :S
预先感谢您:).
推荐答案
您的代码和示例之间有一个主要区别:该示例将numpy
数组作为输入而不是嵌套列表.实际上,在列表中添加np.array(...)
效果很好:
There is one major difference between your code and the example: the example passes a numpy
array as the input rather than a nested list. In fact, adding np.array(...)
around your list works just fine:
cell_rise_Inv= pd.DataFrame(
np.array([[0.00483211, 0.00511619, 0.00891821, 0.0449637, 0.205753],
[0.00520049, 0.00561577, 0.010993, 0.0468998, 0.207461],
[0.00357213, 0.00429087, 0.0132186, 0.0536389, 0.21384],
[-0.0021868, -0.0011312, 0.0120546, 0.0647213, 0.224749],
[-0.0725403, -0.0700884, -0.0382486, 0.0899121, 0.313639]]),
index=[['transition [ns]'] * 5,
[0.0005, 0.001, 0.01, 0.1, 0.5]],
columns=[['capacitance [pF]'] * 5,
[0.01, 0.02, 0.05, 0.1, 0.5]])
我缩短了索引中重复的字符串,并交换了索引级别的顺序,但这些变化不大.
I shortened the repeated strings in the index and swapped the order of the index levels, but those are not significant changes.
编辑
做了一点调查.如果您传递一个嵌套列表(没有np.array
调用),则即使columns
是一维列表,该调用也可以在没有columns
的情况下运行.由于某些原因,除非输入是ndarray
,否则两个元素的嵌套列表不会被解释为多索引.
EDIT
Did a little investigating. If you pass in a nested list (without the np.array
call), the call will work without columns
and even if columns
is a 1D list. For some reason the nested list of two elements is not being interpreted as a multiindex unless the input is an ndarray
.
我根据此问题向熊猫提交了 issue#14467 .
I filed issue #14467 with pandas based on this question.
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