numpy recarray.max()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.max()函数返回记录数组的最大值或沿轴的最大值。
Syntax : numpy.recarray.max(axis=None, out=None, keepdims=False)
Parameters:
axis : [None or int or tuple of ints, optional] Axis or axes along which to operate. By default, flattened input is used.
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.
keepdims : [bool, optional] If this is set to True, the axes which are reduced are left in the result as dimensions with size one. With this option, the result will broadcast correctly against the input array.
Return : [ndarray or scalar] Maximum of record array. If axis is None, the result is a scalar value. If axis is given, the result is an array of dimension arr.ndim – 1.
代码#1：
# Python program explaining
# numpy.recarray.max() 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, 8)],
[(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.max methods
# to float record array along default axis
# i, e along flattened array
out_arr1 = rec_arr.a.max()
# Maximum of the flattened array
print("\nMax of float record array, axis = None : ", out_arr1)
# applying recarray.max methods
# to float record array along axis 0
# i, e along vertical
out_arr2 = rec_arr.a.max(axis = 0)
# Maximum along 0 axis
print("\nMax of float record array, axis = 0 : ", out_arr2)
# applying recarray.max methods
# to float record array along axis 1
# i, e along horizontal
out_arr3 = rec_arr.a.max(axis = 1)
# Maximum along 0 axis
print("\nMax of float record array, axis = 1 : ", out_arr3)
# applying recarray.max methods
# to int record array along default axis
# i, e along flattened array
out_arr4 = rec_arr.b.max()
# Maximum of the flattened array
print("\nMax of int record array, axis = None : ", out_arr4)
# applying recarray.max methods
# to int record array along axis 0
# i, e along vertical
out_arr5 = rec_arr.b.max(axis = 0)
# Maximum along 0 axis
print("\nMax of int record array, axis = 0 : ", out_arr5)
# applying recarray.max methods
# to int record array along axis 1
# i, e along horizontal
out_arr6 = rec_arr.b.max(axis = 1)
# Maximum along 0 axis
print("\nMax of int record array, axis = 1 : ", out_arr6)
Input array : [[( 5., 2) ( 3., -4) ( 6., 8)]
[( 9., 1) ( 5., 4) (-12., -7)]]
Record array of float: [[ 5. 3. 6.]
[ 9. 5. -12.]]
Record array of int: [[ 2 -4 8]
[ 1 4 -7]]
Max of float record array, axis = None : 9.0
Max of float record array, axis = 0 : [9. 5. 6.]
Max of float record array, axis = 1 : [6. 9.]
Max of int record array, axis = None : 8
Max of int record array, axis = 0 : [2 4 8]
Max of int record array, axis = 1 : [8 4]