预测值与残差（含残差图）

def solve():
    import pandas as pd
    import statsmodels.api as sm
    import matplotlib.pyplot as plt
    
    df = pd.read_csv('https://liangdaima.com/static/data/wooldridge/wage1.csv')
    X = sm.add_constant(df['educ'])
    model = sm.OLS(df['wage'], X).fit()
    
    plt.figure(figsize=(10,6))
    plt.scatter(model.fittedvalues, model.resid, alpha=0.5, color='steelblue')
    plt.axhline(y=0, color='r', linestyle='--', linewidth=2)
    plt.title('残差图诊断', fontsize=14)
    plt.xlabel('拟合值', fontsize=12)
    plt.ylabel('残差', fontsize=12)
    plt.grid(alpha=0.3)
    plt.tight_layout()
    plt.show()
    
    print(round(model.resid.mean(), 6))