np.mean()函数

 1. 数组的操作：

import numpy as np
a = np.array([[1, 2], [3, 4]])
print(a)
print(type(a))
print(np.mean(a))
print(np.mean(a, axis=0)) # axis=0，计算每一列的均值
print(np.mean(a, axis=1)) # 计算每一行的均值

2.矩阵的操作

import numpy as np
num1 = np.array([[1,2,3],[2,3,4],[3,4,5],[4,5,6]])

num2 = np.mat(num1)
print(num2)
print(type(num2))
print(np.mean(num2)) # 对所有元素求均值
print(np.mean(num2,0)) # 压缩行，对各列求均值
print(np.mean(num2,1)) # 压缩列，对各行求均值