python中常见函数

版权声明：流浪者 https://blog.csdn.net/gz153016/article/details/85613765

• 1.np.arange
  import numpy as np
  x = np.arange(3)#[0 1 2]
  print(x)
  x = np.arange(3.0)#[0. 1. 2.]
  print(x)
  x = np.arange(3,7)#[3 4 5 6]
  print(x)
  x = np.arange(3,7,2)#[3 5]
  print(x)

• 2.linspace
  import numpy as np
  x = np.linspace(2.0, 3.0, num=5)
  print(x)#[2. 2.25 2.5 2.75 3. ]
  #[2. 2.2 2.4 2.6 2.8]
  x = np.linspace(2.0, 3.0, num=5, endpoint=False)
  print(x)
  x = np.linspace(2.0, 3.0, num=5, retstep=True)
  print(x)
  import matplotlib.pyplot as plt
  N = 5
  y = np.zeros(N)
  x1 = np.linspace(0, 10, N, endpoint=True)
  print(“x1”+str(x1))
  x2 = np.linspace(0, 10, N, endpoint=False)
  print(“x2”+str(x2))
  plt.plot(x1, y, ‘o’)
  plt.plot(x2, y + 0.5, ‘o’)
  plt.ylim([-0.5, 1])
  (-0.5, 1)
  plt.show()

• 3.meshgrid
  import numpy as np
  #np.meshgrid 从坐标向量返回坐标矩阵
  x = np.arange(-2,2)#[-2 -1 0 1]
  y = np.arange(0,3)#[0 1 2]
  #生成一维数组，其实也是向量
  print(“x=”+str(x))
  print(“y=”+str(y))
  z, s = np.meshgrid(x, y)#将两个一维数组变为二维数组
  print(“z=”+str(z))
  print(“s=”+str(s))

“”"
z=[[-2 -1 0 1]
[-2 -1 0 1]
[-2 -1 0 1]]

s=[[0 0 0 0]
[1 1 1 1]
[2 2 2 2]]
“”"
“”"
也就是说，它将 x 变成了矩阵 z 的行向量，
y 变成了矩阵 s 的列向量。
反过来，也是一样的：
“”"
z, s = np.meshgrid(y,x)
print(“z=”+str(z))
print(“s=”+str(s))
“”"
z=[[0 1 2]
[0 1 2]
[0 1 2]
[0 1 2]]
s=[[-2 -2 -2]
[-1 -1 -1]
[ 0 0 0]
[ 1 1 1]]
“”"