1.py

import numpy as np
import matplotlib.pyplot as plt

x_data = [1.0, 2.0, 3.0, 4.0, 5.0]
y_data = [2.0, 4.0, 6.0, 8.0, 10.0]

def forward(x):
    return x * w

def loss(x, y):
    y_pred = forward(x)
    return (y_pred - y) * (y_pred - y)

w_list = []
mse_list = []

for w in np.arange(0.0, 4.1, 0.1):
    print('w=', w)

    l_sum = 0
    for x_val, y_val in zip(x_data, y_data):
        print('w=',w)
        l_sum = 0
        for x_val, y_val in zip(x_data, y_data):
            y_pred_val = forward(x_val)
            loss_val = loss(x_val, y_val)
            l_sum += loss_val
            print('\t', x_val, y_val, y_pred_val, loss_val)
        print('MSE=', l_sum / 3)
        w_list.append(w)
        mse_list.append(l_sum / 3)

plt.plot(w_list, mse_list)
plt.title('MSE vs w')
plt.xlabel('w')
plt.ylabel('MSE')
plt.grid(True)


# 保存图片（推荐）
plt.savefig('./mse_vs_w.png', dpi=200, bbox_inches='tight')
print("✅ 图形已保存为 mse_vs_w.png")

plt.show()