numpy recarray.cumprod()函数| Python
在 numpy 中，数组可能具有包含字段的数据类型，类似于电子表格中的列。一个例子是[(a, int), (b, float)] ，其中数组中的每个条目都是一对 (int, float)。通常，使用诸如arr['a'] and arr['b']类的字典查找来访问这些属性。记录数组允许使用arr.a and arr.b作为数组成员访问字段。
numpy.recarray.cumprod()函数返回给定轴上数组元素的累积乘积。
Syntax : numpy.recarray.cumprod(axis=None, dtype=None, out=None)
Parameters:
axis : Axis along which the cumulative product is computed. The default is to compute the product of the flattened array.
dtype : Type of the returned array, as well as of the accumulator in which the elements are multiplied.
out : [ndarray, optional] A location into which the result is stored.
-> If provided, it must have a shape that the inputs broadcast to.
-> If not provided or None, a freshly-allocated array is returned.
Return : A new array holding the result is returned unless out is specified, in which case it is returned.
代码#1：
# Python program explaining
# numpy.recarray.cumprod() method
# importing numpy as geek
import numpy as geek
# creating input array with 2 different field
in_arr = geek.array([[(5.0, 2), (3.0, -4), (6.0, 9)],
[(9.0, 1), (5.0, 4), (-12.0, -7)]],
dtype =[('a', float), ('b', int)])
print ("Input array : ", in_arr)
# convert it to a record array,
# using arr.view(np.recarray)
rec_arr = in_arr.view(geek.recarray)
print("Record array of float: ", rec_arr.a)
print("Record array of int: ", rec_arr.b)
# applying recarray.cumprod methods
# to float record array along axis 1
out_arr = rec_arr.a.cumprod( axis = 1)
print ("Output array along axis 1: ", out_arr)
# applying recarray.cumprod methods
# to int record array along axis 0
out_arr = rec_arr.b.cumprod(axis = 0)
print ("Output array along axis 0: ", out_arr)
Input array : [[( 5., 2) ( 3., -4) ( 6., 9)]
[( 9., 1) ( 5., 4) (-12., -7)]]
Record array of float: [[ 5. 3. 6.]
[ 9. 5. -12.]]
Record array of int: [[ 2 -4 9]
[ 1 4 -7]]
Output array along axis 1: [[ 5. 15. 90.]
[ 9. 45. -540.]]
Output array along axis 0: [[ 2 -4 9]
[ 2 -16 -63]]