绘制碎石图

def solve():
    import matplotlib
    matplotlib.use('Agg')
    import matplotlib.pyplot as plt
    from sklearn.datasets import load_iris
    from sklearn.decomposition import PCA
    from sklearn.preprocessing import StandardScaler
    iris = load_iris()
    X = iris.data
    scaler = StandardScaler()
    X_s = scaler.fit_transform(X)
    pca = PCA()
    pca.fit(X_s)
    plt.figure(figsize=(8, 5))
    plt.plot(range(1, 5), pca.explained_variance_ratio_, 'bo-')
    plt.xlabel('Components')
    plt.ylabel('Explained Variance Ratio')
    plt.title('Scree Plot')
    plt.tight_layout()
    plt.show()
    print(len(pca.explained_variance_ratio_))