Python中的 numpy.bincount()

在 +ve 整数数组中，numpy.bincount() 方法计算每个元素的出现次数。每个 bin 值是其索引的出现。也可以相应地设置 bin 大小。
句法 ：

numpy.bincount(arr, weights = None, min_len = 0)

参数 ：

arr     : [array_like, 1D]Input array, having positive numbers
weights : [array_like, optional]same shape as that of arr
min_len : Minimum number of bins we want in the output array

返回 ：

Output array with no. of occurrence of index value of bin in input - arr. 
Output array, by default is of the length max element of arr + 1. 
Here size of the output array would be max(input_arr)+1.

代码 1：bincount() 在 NumPy 中的工作

# Python Program explaining 
# working of numpy.bincount() method
  
import numpy as geek
  
# 1D array with +ve integers
array1 = [1, 6, 1, 1, 1, 2, 2]
bin = geek.bincount(array1)
print("Bincount output  : \n ", bin)
print("size of bin : ", len(bin), "\n")
  
array2 = [1, 5, 5, 5, 4, 5, 5, 2, 2, 2]
bin = geek.bincount(array2)
print("Bincount output  : \n ", bin)
print("size of bin : ", len(bin), "\n")
  
# using min_length attribute
length = 10
bin1 = geek.bincount(array2, None, length)
print("Bincount output  : \n ", bin1)
  
print("size of bin : ", len(bin1), "\n")

输出 ：

Bincount output  : 
  [0 4 2 0 0 0 1]
size of bin :  7 

Bincount output  : 
  [0 1 3 0 1 5]
size of bin :  6 

Bincount output  : 
  [0 1 3 0 1 5 0 0 0 0]
size of bin :  10 

代码 2：我们可以根据带有 bincount() 权重的元素执行加法

# Python Program explaining 
# working of numpy.bincount() method
  
import numpy as geek
  
# 1D array with +ve integers
array2 = [10, 11, 4, 6, 2, 1, 9]
array1 = [1, 3, 1, 3, 1, 2, 2]
  
# array2 : weight
bin = geek.bincount(array1, array2)
print("Summation element-wise : \n", bin)
  
#index 0 : 0
#index 1 : 10 + 4 + 2 = 16
#index 2 : 1 + 9 = 10
#index 3 : 11 + 6 = 17

输出 ：

Summation element-wise : 
 [  0.  16.  10.  17.]