第1次作业－Numpy练习

1.创建一个边界值为1而内部都是0的数组，图例如下：
[提示：]解此题可以先把所有值都设置为1，这是大正方形；其次，把边界除外小正方形全部设置为0。
本题用到numpy的切片原理。多维数组同样遵循x[start:stop:step]的原理。
[1. 1. 1. 1. 1. 1. 1. 1. 1. 1.]
[1. 0. 0. 0. 0. 0. 0. 0. 0. 1.]
[1. 0. 0. 0. 0. 0. 0. 0. 0. 1.]
[1. 0. 0. 0. 0. 0. 0. 0. 0. 1.]
[1. 0. 0. 0. 0. 0. 0. 0. 0. 1.]
[1. 0. 0. 0. 0. 0. 0. 0. 0. 1.]
[1. 0. 0. 0. 0. 0. 0. 0. 0. 1.]
[1. 0. 0. 0. 0. 0. 0. 0. 0. 1.]
[1. 0. 0. 0. 0. 0. 0. 0. 0. 1.]
[1. 1. 1. 1. 1. 1. 1. 1. 1. 1.]

import numpy as np
x=np.ones((10,10),float)    
x[1:9,1:9]=0               
print(x)

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

2.在数组主对角线上创建一个值为1,2,3,4的5x5矩阵，图例如下：

[1 0 0 0]
[0 2 0 0]
[0 0 3 0]
[0 0 0 4]

import numpy as np
x = np.zeros((4,4),int)
for i in range(4):
     x[i][i]=i+1
print(x)

[[1 0 0 0]
 [0 2 0 0]
 [0 0 3 0]
 [0 0 0 4]]

3.数组归一化操作
生成一个随机的5*5矩阵，找出最大值和最小值，然后把最大值和最小值分别用1和0表示，其他值则介于在0和1中间。

import numpy as np
x= np.random.rand(5,5)
x[x==x.max()]=1
x[x==x.min()]=0
print(x)

[[0.65154072 0.46461803 0.10025847 0.06711102 0.55334367]
 [0.47071807 0.84528973 0.66444416 0.12416244 0.50521493]
 [0.21249511 0.78451422 0.81287519 0.39334227 0.39661145]
 [0.22717698 0.45865094 0.87537907 0.44365364 0.20876922]
 [0.         0.22548006 1.         0.12399962 0.73217884]]