宜春市城市建设网站百度竞价排名利弊

• 假设我们有一个样本矩阵X，每一列表示一个样本，现在我们要把样本转换成均值为0，方差为1的样本矩阵
  $$\begin{array}{c}{X}_{standard}=\frac{X-\mu }{s}\end{array}$$
• python 测试代码如下：

import numpy as npnp.set_printoptions(suppress=True, precision=3)class MeanVarianceMatrix(object):def __init__(self, matrix):self.matrix = matrixself.standard_matrix = np.zeros_like(self.matrix)def get_standard_matrix(self):my_mean = np.mean(self.matrix, axis=0)my_std = np.std(self.matrix, axis=0)self.standard_matrix = (self.matrix - my_mean) / my_stdcheck_mean = np.mean(self.standard_matrix)check_var = np.var(self.standard_matrix)print(f"*"*50)print(f"matrix=\n{self.matrix}")print(f"standard_matrix=\n{self.standard_matrix}")print(f"check_mean={round(check_mean)}")print(f"check_var={round(check_var)}")print(f"*"*50)if __name__ == "__main__":my_matrix_list = [np.random.randint(1, 20, (3, 3)) for _ in range(5)]my_matrix = np.random.randint(1, 10, (3, 3))for i_matrix in my_matrix_list:my_stand = MeanVarianceMatrix(i_matrix)my_stand.get_standard_matrix()

• 结果如下：

**************************************************
matrix=
[[ 8 10  9][ 7  9 19][ 1 15  1]]
standard_matrix=
[[ 0.863 -0.508 -0.091][ 0.539 -0.889  1.268][-1.402  1.397 -1.177]]
check_mean=0
check_var=1
**************************************************
**************************************************
matrix=
[[13  7 18][12  2  4][16  6 11]]
standard_matrix=
[[-0.392  0.926  1.225][-0.981 -1.389 -1.225][ 1.373  0.463  0.   ]]
check_mean=0
check_var=1
**************************************************
**************************************************
matrix=
[[19 16  1][10  9  1][10 13 10]]
standard_matrix=
[[ 1.414  1.162 -0.707][-0.707 -1.279 -0.707][-0.707  0.116  1.414]]
check_mean=0
check_var=1
**************************************************
**************************************************
matrix=
[[ 4  5 12][ 8 13  5][ 6  6  7]]
standard_matrix=
[[-1.225 -0.843  1.359][ 1.225  1.405 -1.019][ 0.    -0.562 -0.34 ]]
check_mean=0
check_var=1
**************************************************
**************************************************
matrix=
[[ 5 14 17][ 6 10  4][11 11  5]]
standard_matrix=
[[-0.889  1.373  1.411][-0.508 -0.981 -0.79 ][ 1.397 -0.392 -0.621]]
check_mean=0
check_var=1
**************************************************