Question

我有一个关于如何按给定列对整个数组/重新排列进行排序的相当简单的问题。例如，给定数组：

import numpy as np
data = np.array([[5,2], [4,1], [3,6]])

我想按第一列排序数据：

array([[3,6], [4,1], [5,2]])

Answer 1

使用data[np.argsort(data[:, 0])]，其中0是要对其进行排序的列索引：

In [27]: import numpy as np

In [28]: data = np.array([[5,2], [4,1], [3,6]])

In [29]: col = 0

In [30]: data=data[np.argsort(data[:,col])]
Out[30]: 
array([[3, 6],
       [4, 1],
       [5, 2]])

Answer 2

您正在寻找operator.itemgetter

>>> from operator import itemgetter, attrgetter

>>> sorted(student_tuples, key=itemgetter(2))
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]

>>> sorted(student_objects, key=attrgetter('age'))
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]

即

In [7]: a
Out[7]: [[5, 2], [4, 1], [3, 6]]

In [8]: sorted(a, key=operator.itemgetter(0))
Out[8]: [[3, 6], [4, 1], [5, 2]]

Answer 3

这有点棘手：

data[data[:,0].argsort()]

# data[:,n] -- get entire column of index n
# argsort() -- get the indices that would sort it
# data[data[:,n].argsort()] -- get data array sorted by n-th column

我在这里找到了这个食谱：

http://www.scipy.org/NumPy_for_Matlab_Users

http://mathesaurus.sourceforge.net/matlab-numpy.html

Answer 4

要对第二列进行排序，请使用itemgetter

>>> from operator import itemgetter
>>> data = [[5,2], [4,1], [3,6]]
>>> sorted(data)
[[3, 6], [4, 1], [5, 2]]
>>> sorted(data,key=itemgetter(1))
[[4, 1], [5, 2], [3, 6]]
>>>

Answer 5

以下是适用于切片的扩展程序：

DECLARE @counter int = 1;
DECLARE @date date = '2020-04-29'

WHILE @counter <= 7
BEGIN
    select datefromparts(year(@date), month(@date), @counter); 
    SET @counter = @counter + 1;
END

按行排序：

import numpy as np
x = np.array([[9, 1, 2],
              [5, 3, 4],
              [0, 5, 6]])

按列排序：

x[:, x[1,:].argsort()] # Sort by second row

array([[1, 2, 9]
       [3, 4, 5]
       [5, 6, 0]])

按列对python数组/重新排列进行排序

5 个答案: