使用Python实现生成对角矩阵和对角块矩阵

import matplotlib.pyplot as plt
from itertools import product
def drawMat(x, ax=None):
    M, N = x.shape
    if not ax:
        ax = plt.subplot()
    arrM, arrN = np.arange(M), np.arange(N)
    plt.yticks(arrM+0.5, arrM)
    plt.xticks(arrN+0.5, arrN)
    ax.pcolormesh(x)
    ax.invert_yaxis()
    for i,j in product(range(M),range(N)):
        if x[i,j]!=0:
            ax.text(j+0.2, i+0.55, f"{x[i,j]:.2}")

print(tri(3,5,2,dtype=int))
'''
[[1 1 1 0 0]
 [1 1 1 1 0]
 [1 1 1 1 1]]
'''

>>> np.diagflat([1,2,3])
array([[1, 0, 0],
       [0, 2, 0],
       [0, 0, 3]])
>>> np.diag([1,2,3])
array([[1, 0, 0],
       [0, 2, 0],
       [0, 0, 3]])
>>> np.diag(np.ones([3,3])) #提取对角元素
array([1., 1., 1.])

fig = plt.figure()
mats = {
    351:np.tri(3,5,1),
    352:np.tri(3,5,2),
    353:np.tri(3,5,3)
}
for i,key in enumerate(mats, 1):
    ax = fig.add_subplot(1,3,i)
    drawMat(mats[key], ax)

​​​​​​​plt.show()

fig = plt.figure()
x = np.arange(12).reshape(4,3)
mats = [np.tril(x,-1),np.triu(x,-1)]
for i,mat in enumerate(mats, 1):
    print(i, mat)
    ax = fig.add_subplot(1,2,i)
    drawMat(mat.astype(float), ax)

plt.show()

from scipy.linalg import *
import numpy as np
A = np.ones([2,2])
B = np.round(np.random.rand(3,3),2)
C = np.diag([1,2,3])
bd = block_diag(A,B,C)
drawMat(bd)
plt.show()