numpy基础运算1

Posted 2021-02-08 ldq1996

# -*- encoding:utf-8 -*-
# Copyright (c) 2015 Shiye Inc.
# All rights reserved.
#
# Author: ldq <[email protected]>
# Date: 2019/2/11 13:41

import numpy as np

a = np.array([0, np.pi/2, np.pi, np.pi/3, np.pi/4])
b = np.arange(4, 8, 2, np.float64)  #[4. 6.]

b2 = b*2  #[ 8. 12.]
b3 = b + 10  #[14. 16.]
b4 = b ** 2   #[16. 36.]
b5 = b > 5   #[False  True]
b6 = np.sum(b) #10.0
b7 = np.std(b) #1.0

a2 = np.sin(a)   # [0.00000000e+00 1.00000000e+00 1.22464680e-16 8.66025404e-017.07106781e-01]
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# sin cos 的周期为2pi，sin以原点做中心对称，sin(pi/4) = 2 ** (1/2) / 2读作二分之根二
# sin(pi) = 1 , sin(pi/2) = 0
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a3 = np.cos(a)  # [ 1.00000000e+00  6.12323400e-17 -1.00000000e+00  5.00000000e-017.07106781e-01]
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# cos以原点的纵轴做轴对称
# cos(pi) = 0 , cos(pi/2) = 1
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c = np.array([[1, 1], [0, 1]])
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[[1 1]
 [0 1]]
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d = np.arange(4).reshape(2, 2)
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[[0 1]
 [2 3]]
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d2 = np.min(d, axis=0)
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axis=0时以列为查找单元
[0 1]
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d3 = np.std(d, axis=1)
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axis=1时以行为查找单元
[0.5 0.5]
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cd_dot = np.dot(c, d, out=np.array([[1,1], [0,0]]))
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dot矩阵相乘
[[2 4]
 [2 3]]
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cd_dot_2 = c.dot(d)
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dot矩阵相乘
[[2 4]
 [2 3]]
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print(d2)
print(d3)