NumPy 中的 unique函数

此函数在输入数组中返回唯一元素的数组，该函数可以返回唯一值数组和相关索引数组的元组。

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

参数说明，

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]