Python机器学习（四十八）NumPy 矩阵库函数

import numpy.matlib 
import numpy as np 

a = np.matlib.empty((2,2))
print (a)

[[6.91241356e-310 1.37748664e-316]
 [6.91240378e-310 6.91240378e-310]]

import numpy.matlib 
import numpy as np 

a = np.matlib.zeros((2,2))
print (a)

import numpy.matlib 
import numpy as np 

a = np.matlib.zeros((2,2))
print (a)

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

import numpy.matlib 
import numpy as np 

print(‘对角线的开始索引为0：‘)
print(np.matlib.eye(n = 3, M = 4, k = 0, dtype = float))
print(‘\n‘)

print(‘对角线的开始索引为1：‘)
print(np.matlib.eye(n = 3, M = 4, k = 1, dtype = float))
print(‘\n‘)

对角线的开始索引为0：
 [[1. 0. 0. 0.]
  [0. 1. 0. 0.]
  [0. 0. 1. 0.]]

对角线的开始索引为1：
[[0. 1. 0. 0.]
 [0. 0. 1. 0.]
 [0. 0. 0. 1.]]

import numpy.matlib 
import numpy as np 
print (np.matlib.identity(5, dtype = float))

[[ 1.  0.  0.  0.  0.] 
 [ 0.  1.  0.  0.  0.] 
 [ 0.  0.  1.  0.  0.] 
 [ 0.  0.  0.  1.  0.] 
 [ 0.  0.  0.  0.  1.]] 
 ```

 ## numpy.matlib.rand()

`rand()`函数返回一个指定大小的矩阵，其中填充随机值。

**示例**

```python
import numpy.matlib 
import numpy as np 
print (np.matlib.rand(3,3))

[[0.5413199  0.5749519  0.19755942]
 [0.57128833 0.24267348 0.65186677]
 [0.08517    0.9238393  0.15061818]]