极客教程Python Numpy recarray.ppp()函数
在numpy中，数组可以有一个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是一对(int, float)。通常情况下，这些属性使用字典查询，如arr[‘a’] 和 arr[‘b’] 。记录数组允许字段作为数组的成员被访问，使用arr.a和arr.b。
numpy.recarray.tp()函数返回沿给定轴线的峰值至峰值（最大-最小）值。
语法: numpy.recarray.ptp(axis=None, out=None)
参数:
axis : [int, optional] 用于查找峰值的轴。默认情况下，将数组压平。
out : [ndarray, optional] 一个储存结果的位置。
-> 如果提供，它必须有一个输入广播到的形状。
-> 如果没有提供或没有，将返回一个新分配的数组。
返回 : [ndarray] 一个新的数组，用来存放结果，除非指定了out，在这种情况下，将返回对out的引用。
代码#1：
# Python program explaining
# numpy.recarray.ptp() 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.ptp methods
# to float record array along axis 1
out_arr = rec_arr.a.ptp( axis = 1)
print ("Output range array of float along axis 1: ", out_arr)
# applying recarray.ptp methods
# to float record array along axis 0
out_arr = rec_arr.a.ptp( axis = 0)
print ("Output range array of float along axis 0: ", out_arr)
# applying recarray.ptp methods
# to float record array along -1 axis
out_arr = rec_arr.a.ptp( axis = -1)
print ("Output range array of float along -1 axis : ", out_arr)
# applying recarray.ptp methods
# to int record array along default axis value
out_arr = rec_arr.a.ptp()
print ("Output range of float array elements array along default axis: ", out_arr)
# applying recarray.ptp methods
# to int record array along axis 1
out_arr = rec_arr.b.ptp( axis = 1)
print ("Output range array of int along axis 1: ", out_arr)
# applying recarray.ptp methods
# to int record array along axis 0
out_arr = rec_arr.b.ptp( axis = 0)
print ("Output range array of int along axis 0: ", out_arr)
# applying recarray.ptp methods
# to int record array along -1 axis
out_arr = rec_arr.b.ptp( axis = -1)
print ("Output range array of int along -1 axis : ", out_arr)
# applying recarray.ptp methods
# to int record array along default axis value
out_arr = rec_arr.b.ptp()
print ("Output range of int array elements array along default axis: ", out_arr)
输出:
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 range array of float along axis 1: [ 3. 21.]
Output range array of float along axis 0: [ 4. 2. 18.]
Output range array of float along -1 axis : [ 3. 21.]
Output range of float array elements array along default axis: 21.0
Output range array of int along axis 1: [13 11]
Output range array of int along axis 0: [ 1 8 16]
Output range array of int along -1 axis : [13 11]
Output range of int array elements array along default axis: 16