เพอร์เซ็ปตรอน | ตัวจำแนกเชิงเส้นที่เรียบง่ายที่สุด

from __future__ import annotations

import japanize_matplotlib
import matplotlib.pyplot as plt
import numpy as np
from sklearn.datasets import make_blobs
from sklearn.metrics import accuracy_score


def run_perceptron_demo(
    n_samples: int = 200,
    lr: float = 0.1,
    n_epochs: int = 20,
    random_state: int = 0,
    title: str = "เส้นแบ่งของเพอร์เซ็ปตรอน",
    xlabel: str = "คุณลักษณะที่ 1",
    ylabel: str = "คุณลักษณะที่ 2",
    label_boundary: str = "เส้นแบ่ง",
) -> dict[str, object]:
    """Train a perceptron on synthetic blobs and plot the decision boundary."""
    japanize_matplotlib.japanize()
    X, y = make_blobs(
        n_samples=n_samples,
        centers=2,
        cluster_std=1.0,
        random_state=random_state,
    )
    y_signed = np.where(y == 0, -1, 1)

    w = np.zeros(X.shape[1])
    b = 0.0
    history: list[int] = []

    for _ in range(n_epochs):
        errors = 0
        for xi, target in zip(X, y_signed):
            update = lr * target if target * (np.dot(w, xi) + b) <= 0 else 0.0
            if update != 0.0:
                w += update * xi
                b += update
                errors += 1
        history.append(int(errors))
        if errors == 0:
            break

    preds = np.where(np.dot(X, w) + b >= 0, 1, -1)
    accuracy = float(accuracy_score(y_signed, preds))

    xx = np.linspace(X[:, 0].min() - 1, X[:, 0].max() + 1, 200)
    yy = -(w[0] * xx + b) / w[1]

    fig, ax = plt.subplots(figsize=(6, 5))
    ax.scatter(X[:, 0], X[:, 1], c=y, cmap="coolwarm", edgecolor="k")
    ax.plot(xx, yy, color="black", linewidth=2, label=label_boundary)
    ax.set_xlabel(xlabel)
    ax.set_ylabel(ylabel)
    ax.set_title(title)
    ax.legend(loc="best")
    fig.tight_layout()
    plt.show()

    return {"weights": w, "bias": b, "errors": history, "accuracy": accuracy}


metrics = run_perceptron_demo(
    title="เส้นแบ่งของเพอร์เซ็ปตรอน",
    xlabel="คุณลักษณะที่ 1",
    ylabel="คุณลักษณะที่ 2",
    label_boundary="เส้นแบ่ง",
)
print(f"ความแม่นยำขณะฝึก: {metrics['accuracy']:.3f}")
print("น้ำหนัก:", metrics["weights"])
print(f"ไบแอส: {metrics['bias']:.3f}")
print("จำนวนข้อผิดพลาดในแต่ละ epoch:", metrics["errors"])