NumPy教程：矩阵库（Matrix库numpy.matlib）及python示例

NumPy - 矩阵库

NumPy 包包含一个 Matrix库numpy.matlib。此模块的函数返回矩阵而不是返回ndarray对象。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/5893.html

matlib.empty()

matlib.empty()函数返回一个新的矩阵，而不初始化元素。 该函数接受以下参数。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/5893.html

numpy.matlib.empty(shape, dtype, order)

其中：文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/5893.html

示例

import numpy.matlib 
import numpy as np 
print np.matlib.empty((2,2))  
# 填充为随机数据

输出如下：文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/5893.html

[[ 2.12199579e-314,   4.24399158e-314] 
 [ 4.24399158e-314,   2.12199579e-314]]

numpy.matlib.zeros()

此函数返回以零填充的矩阵。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/5893.html

import numpy.matlib 
import numpy as np 
print np.matlib.zeros((2,2))

输出如下：文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/5893.html

[[ 0.  0.] 
 [ 0.  0.]])

numpy.matlib.ones()

此函数返回以一填充的矩阵。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/5893.html

import numpy.matlib 
import numpy as np 
print np.matlib.ones((2,2))

输出如下：文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/5893.html

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

numpy.matlib.eye()

这个函数返回一个矩阵，对角线元素为 1，其他位置为零。 该函数接受以下参数。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/5893.html

numpy.matlib.eye(n, M,k, dtype)

其中：文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/5893.html

示例

import numpy.matlib 
import numpy as np 
print np.matlib.eye(n =  3, M =  4, k =  0, dtype =  float)

输出如下：文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/5893.html

[[ 1.  0.  0.  0.] 
 [ 0.  1.  0.  0.] 
 [ 0.  0.  1.  0.]])

numpy.matlib.identity()

numpy.matlib.identity()函数返回给定大小的单位矩阵。单位矩阵是主对角线元素都为 1 的方阵。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/5893.html

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

输出如下：文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/5893.html

[[ 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()

·numpy.matlib.rand()`函数返回给定大小的填充随机值的矩阵。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/5893.html

示例

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

输出如下：文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/5893.html

[[ 0.82674464  0.57206837  0.15497519] 
 [ 0.33857374  0.35742401  0.90895076] 
 [ 0.03968467  0.13962089  0.39665201]]

注意，矩阵总是二维的，而ndarray是一个 n 维数组。 两个对象都是可互换的。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/5893.html

示例

import numpy.matlib 
import numpy as np  

i = np.matrix('1,2;3,4')  
print i

输出如下：文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/5893.html

[[1  2] 
 [3  4]]

示例

import numpy.matlib 
import numpy as np  

j = np.asarray(i)  
print j

输出如下：文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/5893.html

[[1  2] 
 [3  4]]

示例

import numpy.matlib 
import numpy as np  

k = np.asmatrix (j)  
print k

输出如下：文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/5893.html

[[1  2] 
 [3  4]]