Python3Numpy——相关性协方差应用

2018-06-22 00:59:47来源:未知 阅读 ()

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 基本理论

Correlation

Are there correlations between variables?

Correlation measures the strength of the linear association between two numerical variables. For example, you could imagine that for children, age correlates with height: the older the child, the taller he or she is. You could reasonably expect to get a straight line or upward curve with a positive slope when you plot age against height.

定义

 

生物是一个有机的整体,其各个组成部分都是相关联的,我们可以通过研究一个生物的牙齿、爪子或者骨骼来复原这个生物。

协方差:

定义:

 

对于离散型随机变量:

 

对于连续性随机变量:

 

协方差化简:

 

当X与Y独立时, 有Cov(X, Y) = 0

协方差基本性质:

 

随机变量和的方差与协方差的关系:

D(X +/- Y) = D(X) + D(Y) +/- 2Cov(X, Y)

协方差的有界性

 

相关系数:

定义

 

Python3NumPy关于相关性协方差阐述

导入相关模块

import numpy as np
from matplotlib.pyplot import plot
from matplotlib.pyplot import show
import matplotlib.pyplot as plt

导入数据

bhp = np.loadtxt('BHP.csv', delimiter=',', usecols=(6,), unpack=True)

数据BHP.csv文件如下:

BHP

11-02-2011

 

93.11

94.26

92.9

93.72

1741900

BHP

14-02-2011

 

94.57

96.23

94.39

95.64

2620800

BHP

15-02-2011

 

94.45

95.47

93.91

94.56

2461300

BHP

16-02-2011

 

92.67

93.58

92.56

93.3

3270900

BHP

17-02-2011

 

92.65

93.98

92.58

93.93

2650200

BHP

18-02-2011

 

92.34

93

92

92.39

4667300

BHP

22-02-2011

 

93.14

93.98

91.75

92.11

5359800

BHP

23-02-2011

 

91.93

92.46

91.05

92.36

7768400

BHP

24-02-2011

 

92.42

92.71

90.93

91.76

4799100

BHP

25-02-2011

 

93.48

94.04

92.44

93.91

3448300

BHP

28-02-2011

 

94.81

95.11

94.1

94.6

4719800

BHP

01-03-2011

 

95.05

95.2

93.13

93.27

3898900

BHP

02-03-2011

 

93.89

94.89

93.54

94.43

3727700

BHP

03-03-2011

 

95.9

96.11

95.18

96.02

3379400

BHP

04-03-2011

 

96.12

96.44

95.08

95.76

2463900

BHP

07-03-2011

 

96.51

96.66

94.03

94.47

3590900

BHP

08-03-2011

 

93.72

94.47

92.9

94.34

3805000

BHP

09-03-2011

 

92.94

93.13

91.86

92.22

3271700

BHP

10-03-2011

 

89

89.17

87.93

88.31

5507800

BHP

11-03-2011

 

88.24

89.8

88.16

89.59

2996800

BHP

14-03-2011

 

88.17

89.06

87.82

89.02

3434800

BHP

15-03-2011

 

84.58

87.32

84.35

86.95

5008300

BHP

16-03-2011

 

86.31

87.28

83.85

84.88

7809799

BHP

17-03-2011

 

87.32

88.29

86.89

87.38

3947100

BHP

18-03-2011

 

89.53

89.58

88.05

88.56

3809700

BHP

21-03-2011

 

90.13

90.16

88.88

89.59

3098200

BHP

22-03-2011

 

89.5

89.59

88.42

88.71

3500200

BHP

23-03-2011

 

89.57

90.32

88.85

90.02

4285600

BHP

24-03-2011

 

90.86

91.35

89.7

91.26

3918800

BHP

25-03-2011

 

90.42

91.09

90.07

90.67

3632200

vale = np.loadtxt('VALE.csv', delimiter=',', usecols=(6,), unpack=True)

数据VALE.csv文件如下:

VALE

11-02-2011

 

33.88

34.54

33.63

34.37

18433500

VALE

14-02-2011

 

34.53

35.29

34.52

35.13

20780700

VALE

15-02-2011

 

34.89

35.31

34.82

35.14

17756700

VALE

16-02-2011

 

35.16

35.4

34.81

35.31

16792800

VALE

17-02-2011

 

35.18

35.6

35.04

35.57

24088300

VALE

18-02-2011

 

35.31

35.37

34.89

35.03

21286600

VALE

22-02-2011

 

33.94

34.57

33.36

33.44

28364700

VALE

23-02-2011

 

33.43

34.12

33.1

33.94

22559300

VALE

24-02-2011

 

34.3

34.3

33.56

34.21

20591900

VALE

25-02-2011

 

34.67

34.95

34.05

34.27

20151500

VALE

28-02-2011

 

34.34

34.51

33.7

34.23

16126000

VALE

01-03-2011

 

34.39

34.44

33.68

33.76

17282400

VALE

02-03-2011

 

33.61

34.5

33.57

34.32

15870900

VALE

03-03-2011

 

34.77

34.89

34.53

34.87

14648200

VALE

04-03-2011

 

34.67

34.83

34.04

34.5

15330800

VALE

07-03-2011

 

34.43

34.53

32.97

33.23

25040500

VALE

08-03-2011

 

33.22

33.7

32.55

33.29

17093000

VALE

09-03-2011

 

33.23

33.44

32.68

32.88

20026300

VALE

10-03-2011

 

32.17

32.4

31.68

31.91

30803900

VALE

11-03-2011

 

31.53

32.42

31.49

32.17

24429900

VALE

14-03-2011

 

32.03

32.45

31.74

32.44

15525500

VALE

15-03-2011

 

30.99

31.93

30.79

31.91

24767700

VALE

16-03-2011

 

31.99

32.03

30.68

31.04

30394153

VALE

17-03-2011

 

31.44

31.82

31.32

31.51

24035000

VALE

18-03-2011

 

32.17

32.39

31.98

32.14

19740600

VALE

21-03-2011

 

32.81

32.85

32.26

32.42

18923700

VALE

22-03-2011

 

32.13

32.32

31.74

32.25

18934200

VALE

23-03-2011

 

32.39

32.91

32.22

32.7

18359900

VALE

24-03-2011

 

32.82

32.94

32.12

32.36

25894100

VALE

25-03-2011

 

32.26

32.74

31.93

32.34

16688900

数据处理:

bhp_returns = np.diff(bhp) / bhp[:-1]
vale_returns = np.diff(vale) / vale[:-1]

计算bhp_returns和vale_returns的协方差

covariance = np.cov(bhp_returns, vale_returns)
print(covariance)

结果:

[[0.00028179 0.00019766]
 [0.00019766 0.00030123]]

取协方差对角线上的元素:

print(covariance.diagonal())

结果:

[0.00028179 0.00030123]

打印协方差矩阵的迹:

print(covariance.trace())

结果:

0.000583023549920278

计算bhp_returns和vale_returns的相关系数:

print(covariance/((bhp_returns.std()*vale_returns.std())))

结果:

[[1.00173366 0.70264666]
 [0.70264666 1.0708476 ]]
print(np.corrcoef(bhp_returns, vale_returns))

结果:

[[1.         0.67841747]
 [0.67841747 1.        ]]

绘bhp_returns和vale_returns的图像:

t = np.arange(len(bhp_returns))
plot(t, bhp_returns, lw = 1)
plot(t, vale_returns,lw =2)
show()

 结果:

相关知识点理解

np.diff(a, n=1, axis=-1)

沿着指定轴计算第N维的离散差值 
参数: 
a:输入矩阵 
n:可选,代表要执行几次差值 
axis:默认是最后一个 
示例:
import numpy as np
A = np.arange(2 , 14).reshape((3 , 4))
A[1 , 1] = 8
print('A:' , A)
# A: [[ 2 3 4 5]
# [ 6 8 8 9]
# [10 11 12 13]]
print(np.diff(A))
# [[1 1 1]
# [2 0 1]
# [1 1 1]]
从输出结果可以看出,其实diff函数就是执行的是后一个元素减去前一个元素

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