[英]Pandas reshape dataframe every N rows to columns
I have a dataframe as follows : 我有一个数据帧如下:
df1=pd.DataFrame(np.arange(24).reshape(6,-1),columns=['a','b','c','d'])
and I want to take 3 set of rows and convert them to columns with following order 我想采取3组行,并按照以下顺序将它们转换为列
pd.DataFrame(np.reshape(df1.values,(3,-1)),columns=['a','b','c','d','e','f','g','h'])
In [258]: df = pd.DataFrame(np.hstack(np.split(df1, 2)))
In [259]: df
Out[259]:
0 1 2 3 4 5 6 7
0 0 1 2 3 12 13 14 15
1 4 5 6 7 16 17 18 19
2 8 9 10 11 20 21 22 23
In [260]: import string
In [261]: df.columns = list(string.ascii_lowercase[:len(df.columns)])
In [262]: df
Out[262]:
a b c d e f g h
0 0 1 2 3 12 13 14 15
1 4 5 6 7 16 17 18 19
2 8 9 10 11 20 21 22 23
Create 3d array by reshape
: 通过
reshape
创建3d数组:
a = np.hstack(np.reshape(df1.values,(-1, 3, len(df1.columns))))
df = pd.DataFrame(a,columns=['a','b','c','d','e','f','g','h'])
print (df)
a b c d e f g h
0 0 1 2 3 12 13 14 15
1 4 5 6 7 16 17 18 19
2 8 9 10 11 20 21 22 23
This uses the reshape/swapaxes/reshape
idiom for rearranging sub-blocks of NumPy arrays. 这使用
reshape/swapaxes/reshape
惯用法来重新排列NumPy数组的子块。
In [26]: pd.DataFrame(df1.values.reshape(2,3,4).swapaxes(0,1).reshape(3,-1), columns=['a','b','c','d','e','f','g','h'])
Out[26]:
a b c d e f g h
0 0 1 2 3 12 13 14 15
1 4 5 6 7 16 17 18 19
2 8 9 10 11 20 21 22 23
If you want a pure pandas solution: 如果你想要一个纯粹的熊猫解决方案:
df.set_index([df.index % 3, df.index // 3])\
.unstack()\
.sort_index(level=1, axis=1)\
.set_axis(list('abcdefgh'), axis=1, inplace=False)
Output: 输出:
a b c d e f g h
0 0 1 2 3 12 13 14 15
1 4 5 6 7 16 17 18 19
2 8 9 10 11 20 21 22 23
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