Python Numpy recarray.argmin()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.argmin()函数返回数组中最小元素在特定轴中的索引。
语法: numpy.recarray.argmin(axis=None, out=None)
参数:
axis : [ int, optional] 沿着一个指定的轴,如0或1
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 of ints] 与array.shape相同形状的数组的索引数,去掉了沿轴的尺寸。
代码#1:
# Python program explaining
# numpy.recarray.argmin() 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.argmin methods to
# float record array along axis 1
out_arr = geek.recarray.argmin(rec_arr.a, axis = 1)
print ("Output array along axis 1: ", out_arr)
# applying recarray.argmin methods to
# int record array along axis 0
out_arr = geek.recarray.argmin(rec_arr.b, axis = 0)
print ("Output array along axis 0: ", out_arr)
输出:
Input array : [[(5.0, 2) (3.0, 4) (6.0, 9)]
[(9.0, 1) (5.0, 4) (-12.0, -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: [1 2]
Output array along axis 0: [1 0 1]
代码#2:
如果我们将numpy.recarray.argmin()应用于整个记录数组,则会产生Type错误
# Python program explaining
# numpy.recarray.argmin() 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, -7)],
[(9.0, 1), (6.0, 4), (-2.0, -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)
# applying recarray.argmin methods to record array
out_arr = geek.recarray.argmin(rec_arr)
输出:
TypeError: Cannot cast array data from dtype((numpy.record, [(‘a’, ‘<f8′), (‘b’, ‘<i8’)])) to dtype(‘V16’) according to the rule ‘safe’