Numpy recarray.compress()函数| Python
原文:https://www . geeksforgeeks . org/numpy-recarray-compress-function-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)]，数组中的每个条目都是一对(int，float)。通常，这些属性是使用字典查找来访问的，例如arr['a'] and arr['b']。
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.compress() 函数返回沿给定轴排列的选定切片。
语法:
numpy.recarray.compress(condition, axis=None, out=None)参数: 条件:【布尔一维数组】选择返回哪些条目的数组。 轴:【int，可选】切片所沿的轴。 出:结果会放在这个阵中。
返回: compressed_array，ndarray。
代码#1 :
# Python program explaining
# numpy.recarray.compress() 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 int: ", rec_arr.b)
# applying recarray.compress methods to float record array
float_rec_arr = rec_arr.a
print("Record array of float: ", float_rec_arr)
out_arr = (rec_arr.a).compress([0, 1], axis = 0)
print ("Output compressed array : ", out_arr)
# applying recarray.compress methods to int record array
int_rec_arr = rec_arr.b
print("Record array of int: ", int_rec_arr)
out_arr = int_rec_arr.compress([True, False], axis = 1)
print ("Output compressed array : ", out_arr)
Output:
Input array : [[(5.0, 2) (3.0, -4) (6.0, 9)]
[(9.0, 1) (5.0, 4) (-12.0, -7)]]
Record array of int: [[ 2 -4 9]
[ 1 4 -7]]
Record array of float: [[ 5\. 3\. 6.]
[ 9\. 5\. -12.]]
Output compressed array : [[ 9\. 5\. -12.]]
Record array of int: [[ 2 -4 9]
[ 1 4 -7]]
Output compressed array : [[2]
[1]]
代码#2 :
# Python program explaining
# numpy.recarray.compress() 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 int: ", rec_arr.b)
# applying recarray.compress methods to whole record array
out_arr = rec_arr.compress([True, False], axis = 1)
print ("Output compressed array : ", out_arr)
Output:
Input array : [[(5.0, 2) (3.0, -4) (6.0, 9)]
[(9.0, 1) (5.0, 4) (-12.0, -7)]]
Record array of int: [[ 2 -4 9]
[ 1 4 -7]]
Output compressed array : [[(5.0, 2)]
[(9.0, 1)]]
