generated from LufsX/Experiment-kNN
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# function.py
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import numpy as np
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import os
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from sklearn.preprocessing import StandardScaler # 导入标准化库
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# 学号和姓名
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"""
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实验说明:
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- 自行编写实现数据加载与 kNN 的手写数字分类算法。
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- 函数输入: 待分类的样本 input_vector, 训练数据集 dataSet, 训练集对应的标签 labels。
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- 函数返回: 预测的分类标签。
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注意事项:
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- 在 function.py 中实现 kNN 分类算法。
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- 可以自行导入其他库，需要在 requirements.txt 添加依赖，若未在 requirements.txt 中添加使用到的依赖，则无法自动评测，成绩为零。
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- 自动评测脚本仅会加载 classify 和 load_data 函数，请勿修改函数名。
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- 训练集和测试集需手动下载解压，并放入当前目录下。
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测评环境:
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- CPU: Intel Xeon(R) CPU E3-1231 v3 @ 3.40GHz
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- OS: Ubuntu 22.04.4 LTS
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- Python: 3.10.12
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- numpy: 2.1.1
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"""
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"""
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请在这里填写学号和姓名，不填写即成绩无效。
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"""
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id = "202210423119"
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name = "肖锐"
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def sigmoid(z):
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"""计算sigmoid函数"""
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return 1.0 / (1 + np.exp(-z))
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def compute_gradient(X_batch, y_batch, weights, lambda_reg):
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"""计算梯度，包含L2正则化"""
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z = np.dot(X_batch, weights)
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h = sigmoid(z)
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gradient = np.dot(X_batch.T, (h - y_batch)) / len(y_batch)
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gradient += (lambda_reg / len(y_batch)) * weights # L2正则化
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return gradient
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"""
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参数说明:
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- input_vector (numpy array): 输入待分类的样本。
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- dataSet (numpy array): 训练数据集。
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- labels (list or numpy array): 训练集对应的标签。
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- k (int): kNN 算法参数，请**自行设置默认值**，评测时仅会使用其默认值，不修改默认值将**无法通过**评测，**成绩为零**。
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返回值:
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- int: 预测的分类标签。
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"""
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def train_logreg(X, y, learning_rate=0.001, iterations=10000, batch_size=64, lambda_reg=0.1):
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"""对率回归训练函数。"""
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m, n = X.shape
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weights = np.random.randn(n) * np.sqrt(2. / n) # He初始化
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print("开始训练对率回归模型")
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# 这里写自己的代码实现
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def classify(input_vector, dataSet, labels, k=4):
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"""
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KNN 分类算法。
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Args:
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- input_vector (numpy array): 输入待分类的样本。
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- dataSet (numpy array): 训练数据集。
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- labels (list or numpy array): 训练集对应的标签。
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- k (int): kNN 算法参数，请**自行设置默认值**，评测时仅会使用其默认值，不修改默认值将**无法通过**评测，**成绩为零**。
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Returns:
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- int: 预测的分类标签。
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"""
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"""
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使用欧式距离的 kNN 分类算法。
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"""
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# 计算欧式距离
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distances = np.linalg.norm(dataSet - input_vector, axis=1)
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for i in range(iterations):
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indices = np.random.permutation(m)
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X_shuffled = X[indices]
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y_shuffled = y[indices]
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# 获取距离最近的 k 个样本的索引
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k_indices = np.argsort(distances)[:k]
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# 获取最近邻样本的标签
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k_nearest_labels = [labels[i] for i in k_indices]
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# 找出出现次数最多的标签
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most_common = max(set(k_nearest_labels), key=k_nearest_labels.count)
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return most_common
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for j in range(0, m, batch_size):
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X_batch = X_shuffled[j:j + batch_size]
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y_batch = y_shuffled[j:j + batch_size]
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gradient = compute_gradient(X_batch, y_batch, weights, lambda_reg)
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weights -= learning_rate * gradient
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# 这里也写自己的代码实现
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def load_dataset(directory):
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"""
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从文件夹中加载数据，若不自行正确实现，则无法通过评测，**不记录成绩**。
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Args:
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- directory (str): 数据文件夹路径。
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Returns:
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- np.array: 特征数据。
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- np.array: 标签数据。
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"""
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features = []
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labels = []
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# 遍历文件夹中的所有文件
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for filename in os.listdir(directory):
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if filename.endswith(".txt"): # 假设文件是 .txt 格式
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filepath = os.path.join(directory, filename)
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if i % 1000 == 0: # 每1000次迭代打印一次信息
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print(f"迭代 {i}: 当前权重形状: {weights.shape}")
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return weights
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def predict_logreg(inX, weights):
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"""对率回归预测函数。"""
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z = np.dot(inX, weights)
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h = sigmoid(z)
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return 1 if h >= 0.5 else 0
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def load_data(filepath):
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"""从文件中加载数据。"""
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if not os.path.exists(filepath):
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raise FileNotFoundError(f"文件 {filepath} 不存在！")
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# 假设文件名格式为 "数字_编号.txt"
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label = int(filename.split('_')[0])
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# 加载文件中的二进制数据并转换为 1D 向量
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image_vector = img_to_vector(filepath)
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features.append(image_vector)
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labels.append(label)
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data, labels = [], []
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print(f"加载数据中: {filepath}")
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with open(filepath, 'r') as f:
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for line in f:
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line = line.strip().split()
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if len(line) >= 1 and line[-1].isdigit():
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line_data = [0 if x == '?' else float(x) for x in line[:-1]]
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data.append(line_data)
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labels.append(int(line[-1]))
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return np.array(features), np.array(labels)
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data = np.array(data)
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labels = np.array(labels)
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# 这里还写自己的代码实现
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def img_to_vector(filename):
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"""
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将二值图像转换为向量。
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该部分应为 load_dataset 函数的辅助子函数，可单独在这里实现，也可直接集成至 load_dataset 函数中。
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Args:
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- filename (str): 图像文件路径。
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Returns:
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- np.array: 二值图像向量。
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"""
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with open(filename) as file:
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lines = file.readlines()
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image_vector = np.array([int(char) for line in lines for char in line.strip()])
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num_features = data.shape[1]
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indices_to_remove = [2]
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if num_features > 23:
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indices_to_remove.extend(range(23, min(28, num_features)))
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data = np.delete(data, indices_to_remove, axis=1)
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target_variable = np.where((labels == 2) | (labels == 3), 0, 1)
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print(f"数据加载成功，数据形状: {data.shape}, 标签形状: {target_variable.shape}")
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return data, target_variable
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def k_fold_cross_validation(X, y, k=5, learning_rate=0.001, iterations=10000, batch_size=64, lambda_reg=0.1):
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"""K折交叉验证。"""
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m = X.shape[0]
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fold_size = m // k
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accuracies = []
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for i in range(k):
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val_start = i * fold_size
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val_end = (i + 1) * fold_size if i != k - 1 else m
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X_val = X[val_start:val_end]
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y_val = y[val_start:val_end]
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X_train = np.concatenate((X[:val_start], X[val_end:]))
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y_train = np.concatenate((y[:val_start], y[val_end:]))
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weights = train_logreg(X_train, y_train, learning_rate, iterations, batch_size, lambda_reg)
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val_accuracy = np.mean([predict_logreg(X_val[j], weights) == y_val[j] for j in range(len(y_val))])
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accuracies.append(val_accuracy)
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print(f"Fold {i + 1}/{k} - 验证准确率: {val_accuracy:.4f}")
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return np.mean(accuracies)
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return image_vector
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if __name__ == "__main__":
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# 加载训练集
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try:
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X_train, y_train = load_data("./data/horse-colic.data")
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except FileNotFoundError as e:
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print(e)
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exit()
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# 以下代码可用于测试，可自行随意修改
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train_data, train_labels = load_dataset("trainingDigits")
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# 数据归一化处理
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scaler = StandardScaler()
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X_train = scaler.fit_transform(X_train) # 使用训练集进行标准化
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test_data = (
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"00000000000000110000000000000000"
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"00000000000011111000000000000000"
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"00000000000011111100000000000000"
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"00000000001111111110000000000000"
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"00000000001111111110000000000000"
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"00000000001111111100000000000000"
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"00000000011111111000000000000000"
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"00000000111111111000000000000000"
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"00000000111111110000000000000000"
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"00000000111111110000000000000000"
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"00000000111111110000000000000000"
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"00000000111111110000000000000000"
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"00000000111111100000000000000000"
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"00000001111111100000000000000000"
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"00000001111111100000000000000000"
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"00000001111111100000000000000000"
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"00000001111111111111000000000000"
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"00000001111111111111111000000000"
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"00000001111111111111111100000000"
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"00000011111111111111111110000000"
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"00000011111111111111111110000000"
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"00000001111111111111111110000000"
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"00000001111111111111111110000000"
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"00000000111111111100111111100000"
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"00000000111111111000111111100000"
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"00000000011111111001111111100000"
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"00000000011111111111111111000000"
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"00000000001111111111111111000000"
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"00000000000111111111111111000000"
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"00000000000011111111111100000000"
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"00000000000001111111110000000000"
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"00000000000000000111100000000000"
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)
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predicted_label = classify(
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np.array([int(char) for char in test_data]).reshape(1, 1024),
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train_data,
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train_labels,
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)
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# k折交叉验证
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avg_accuracy = k_fold_cross_validation(X_train, y_train, k=5, learning_rate=0.01, iterations=1000)
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print(f"K折交叉验证的平均准确率: {avg_accuracy:.4f}")
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# 加载测试集
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try:
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X_test, y_test = load_data("./data/horse-colic.test")
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except FileNotFoundError as e:
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print(e)
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exit()
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# 测试集也需要进行相同的归一化
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X_test = scaler.transform(X_test) # 使用相同的Scaler进行测试集的标准化
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# 训练对率回归模型
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weights = train_logreg(X_train, y_train, learning_rate=0.01, iterations=1000)
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# 测试单个数据
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y_pred = predict_logreg(X_test[11], weights)
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print(f"预测结果: {y_pred}, 实际结果: {y_test[11]}")
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print(f"预测的标签: {predicted_label}")
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