Question

此函数返回输入数组中的唯一元素数组。 该函数可以返回唯一值数组的数组和关联索引数组。 索引的性质取决于函数调用中返回参数的类型。

numpy.unique(arr, return_index, return_inverse, return_counts)

Where,

Sr.No.	参数和描述
1	arr 输入数组。 如果不是一维阵列，将会变平
2	return_index 如果为True，则返回输入数组中元素的索引
3	return_inverse 如果为True，则返回唯一数组的索引，该索引可用于重建输入数组
4	return_counts 如果为True，则返回唯一数组中的元素出现在原始数组中的次数

例子 (Example)

import numpy as np 
a = np.array([5,2,6,2,7,5,6,8,2,9]) 
print 'First array:' 
print a 
print '\n'  
print 'Unique values of first array:' 
u = np.unique(a) 
print u 
print '\n'  
print 'Unique array and Indices array:' 
u,indices = np.unique(a, return_index = True) 
print indices 
print '\n'  
print 'We can see each number corresponds to index in original array:' 
print a 
print '\n'  
print 'Indices of unique array:' 
u,indices = np.unique(a,return_inverse = True) 
print u 
print '\n' 
print 'Indices are:' 
print indices 
print '\n'  
print 'Reconstruct the original array using indices:' 
print u[indices] 
print '\n'  
print 'Return the count of repetitions of unique elements:' 
u,indices = np.unique(a,return_counts = True) 
print u 
print indices

其输出如下 -

First array:
[5 2 6 2 7 5 6 8 2 9]
Unique values of first array:
[2 5 6 7 8 9]
Unique array and Indices array:
[1 0 2 4 7 9]
We can see each number corresponds to index in original array:
[5 2 6 2 7 5 6 8 2 9]
Indices of unique array:
[2 5 6 7 8 9]
Indices are:
[1 0 2 0 3 1 2 4 0 5]
Reconstruct the original array using indices:
[5 2 6 2 7 5 6 8 2 9]
Return the count of repetitions of unique elements:
[2 5 6 7 8 9]
 [3 2 2 1 1 1]