numpy recarray.ptp()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.ptp()函数沿给定轴返回峰值到峰值（最大值 - 最小值）值。

Syntax : numpy.recarray.ptp(axis=None, out=None)

Parameters:

axis : [int, optional] Axis along which to find the peaks. By default, flatten the array.
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 : [ndarray] A new array holding the result, unless out was specified, in which case a reference to out is returned.

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