DAY36 复习日

我们使用了神经网络的方式，用了pytorch重新对信贷数据集进行处理。

import pandas as pd import numpy as np import torch import torch.nn as nn import torch.optim as optim from torch.utils.data import Dataset, DataLoader from sklearn.model_selection import train_test_split from sklearn.preprocessing import StandardScaler, LabelEncoder from sklearn.metrics import accuracy_score, precision_score, recall_score, roc_auc_score, confusion_matrix import matplotlib.pyplot as plt import seaborn as sns import os # 设置随机种子以保证结果可复现 torch.manual_seed(42) np.random.seed(42) # --- 1. 数据预处理 --- def load_and_preprocess_data(filepath): print("Loading data...") df = pd.read_csv(filepath) # 删除 Id 列 if 'Id' in df.columns: df = df.drop('Id', axis=1) print(f"Original shape: {df.shape}") # 处理 'Current Loan Amount' 异常值 (99999999.0 通常表示无限制或错误) # 替换为 NaN 然后进行插补，或者替换为最大有效值。 # 这里我们替换为 NaN 并使用中位数插补，如果数量太多也可以直接删除。 # 先检查一下数量。 outlier_mask = df['Current Loan Amount'] == 99999999.0 df.loc[outlier_mask, 'Current Loan Amount'] = np.nan # 解析 'Years in current job' # 映射关系: '< 1 year'->0, '1 year'->1, ..., '10+ years'->10 def parse_years(x): if pd.isna(x): return np.nan if '<' in x: return 0 if '+' in x: return 10 return int(x.split()[0]) df['Years in current job'] = df['Years in current job'].apply(parse_years) # 插补缺失值 # 数值列 num_cols = df.select_dtypes(include=[np.number]).columns for col in num_cols: if col != 'Credit Default': # 使用中位数以增强鲁棒性 median_val = df[col].median() df[col].fillna(median_val, inplace=True) # 类别列 cat_cols = df.select_dtypes(include=['object']).columns for col in cat_cols: mode_val = df[col].mode()[0] df[col].fillna(mode_val, inplace=True) # 编码类别变量 (One-Hot 编码) df = pd.get_dummies(df, columns=cat_cols, drop_first=True) print(f"Processed shape: {df.shape}") # 划分数据 X = df.drop('Credit Default', axis=1).values y = df['Credit Default'].values # 70% 训练集, 15% 验证集, 15% 测试集 # 第一次划分: 训练集 (70%) 和 临时集 (30%) X_train, X_temp, y_train, y_temp = train_test_split(X, y, test_size=0.3, random_state=42, stratify=y) # 第二次划分: 验证集 (总量的 15% -> 临时集的 50%) 和 测试集 (总量的 15% -> 临时集的 50%) X_val, X_test, y_val, y_test = train_test_split(X_temp, y_temp, test_size=0.5, random_state=42, stratify=y_temp) # 标准化 scaler = StandardScaler() X_train = scaler.fit_transform(X_train) X_val = scaler.transform(X_val) X_test = scaler.transform(X_test) return X_train, y_train, X_val, y_val, X_test, y_test, df.drop('Credit Default', axis=1).columns # --- 2. PyTorch 数据集 --- class CreditDataset(Dataset): def __init__(self, X, y): self.X = torch.FloatTensor(X) self.y = torch.FloatTensor(y).unsqueeze(1) # 二分类需要 (N, 1) 的形状 def __len__(self): return len(self.X) def __getitem__(self, idx): return self.X[idx], self.y[idx] # --- 3. 神经网络模型 --- class CreditNN(nn.Module): def __init__(self, input_dim): super(CreditNN, self).__init__() # 3 个隐藏层: 128 -> 64 -> 32 self.layer1 = nn.Linear(input_dim, 128) self.relu1 = nn.ReLU() self.dropout1 = nn.Dropout(0.3) self.layer2 = nn.Linear(128, 64) self.relu2 = nn.ReLU() self.dropout2 = nn.Dropout(0.3) self.layer3 = nn.Linear(64, 32) self.relu3 = nn.ReLU() self.output = nn.Linear(32, 1) self.sigmoid = nn.Sigmoid() def forward(self, x): x = self.dropout1(self.relu1(self.layer1(x))) x = self.dropout2(self.relu2(self.layer2(x))) x = self.relu3(self.layer3(x)) x = self.sigmoid(self.output(x)) return x # --- 4. 训练函数 --- def train_model(model, train_loader, val_loader, criterion, optimizer, num_epochs=100, patience=10): train_losses = [] val_losses = [] train_accs = [] val_accs = [] best_val_loss = float('inf') epochs_no_improve = 0 device = torch.device("cuda" if torch.cuda.is_available() else "cpu") model.to(device) print(f"Training on {device}") for epoch in range(num_epochs): model.train() running_loss = 0.0 correct_train = 0 total_train = 0 for X_batch, y_batch in train_loader: X_batch, y_batch = X_batch.to(device), y_batch.to(device) optimizer.zero_grad() outputs = model(X_batch) loss = criterion(outputs, y_batch) loss.backward() optimizer.step() running_loss += loss.item() predicted = (outputs > 0.5).float() total_train += y_batch.size(0) correct_train += (predicted == y_batch).sum().item() epoch_train_loss = running_loss / len(train_loader) epoch_train_acc = correct_train / total_train train_losses.append(epoch_train_loss) train_accs.append(epoch_train_acc) # 验证 model.eval() running_val_loss = 0.0 correct_val = 0 total_val = 0 with torch.no_grad(): for X_batch, y_batch in val_loader: X_batch, y_batch = X_batch.to(device), y_batch.to(device) outputs = model(X_batch) loss = criterion(outputs, y_batch) running_val_loss += loss.item() predicted = (outputs > 0.5).float() total_val += y_batch.size(0) correct_val += (predicted == y_batch).sum().item() epoch_val_loss = running_val_loss / len(val_loader) epoch_val_acc = correct_val / total_val val_losses.append(epoch_val_loss) val_accs.append(epoch_val_acc) print(f"Epoch [{epoch+1}/{num_epochs}] " f"Train Loss: {epoch_train_loss:.4f} Acc: {epoch_train_acc:.4f} | " f"Val Loss: {epoch_val_loss:.4f} Acc: {epoch_val_acc:.4f}") # 早停检查 if epoch_val_loss < best_val_loss: best_val_loss = epoch_val_loss epochs_no_improve = 0 # 保存最佳模型 torch.save(model.state_dict(), 'best_credit_model.pth') else: epochs_no_improve += 1 if epochs_no_improve >= patience: print("Early stopping triggered!") break return train_losses, val_losses, train_accs, val_accs # --- 5. 评估与可视化 --- def evaluate_model(model, test_loader, feature_names): device = torch.device("cuda" if torch.cuda.is_available() else "cpu") model.load_state_dict(torch.load('best_credit_model.pth')) model.to(device) model.eval() y_true = [] y_pred = [] y_scores = [] with torch.no_grad(): for X_batch, y_batch in test_loader: X_batch = X_batch.to(device) outputs = model(X_batch) y_scores.extend(outputs.cpu().numpy()) predicted = (outputs > 0.5).float() y_pred.extend(predicted.cpu().numpy()) y_true.extend(y_batch.numpy()) y_true = np.array(y_true) y_pred = np.array(y_pred) y_scores = np.array(y_scores) # 指标计算 acc = accuracy_score(y_true, y_pred) prec = precision_score(y_true, y_pred) rec = recall_score(y_true, y_pred) auc = roc_auc_score(y_true, y_scores) print("\n--- Test Set Evaluation ---") print(f"Accuracy: {acc:.4f}") print(f"Precision: {prec:.4f}") print(f"Recall: {rec:.4f}") print(f"AUC: {auc:.4f}") # 混淆矩阵 cm = confusion_matrix(y_true, y_pred) plt.figure(figsize=(6, 5)) sns.heatmap(cm, annot=True, fmt='d', cmap='Blues') plt.title('Confusion Matrix') plt.ylabel('True Label') plt.xlabel('Predicted Label') plt.savefig('confusion_matrix.png') print("Saved confusion_matrix.png") # 可视化第一层权重 (特征重要性近似) # 我们取每个输入特征的权重的绝对值均值来观察其贡献 weights = model.layer1.weight.data.cpu().numpy() feature_importance = np.mean(np.abs(weights), axis=0) # 特征排序 sorted_idx = np.argsort(feature_importance)[-10:] # 取前10个 plt.figure(figsize=(10, 6)) plt.barh(range(10), feature_importance[sorted_idx]) plt.yticks(range(10), feature_names[sorted_idx]) plt.xlabel('Mean Absolute Weight') plt.title('Top 10 Feature Importance (Layer 1 Weights)') plt.savefig('feature_importance.png') print("Saved feature_importance.png") # --- 主程序执行 --- if __name__ == "__main__": # 加载数据 data_path = 'e:\\桌面\\Python60DaysChallenge-main\\data.csv' X_train, y_train, X_val, y_val, X_test, y_test, feature_names = load_and_preprocess_data(data_path) # 创建 DataLoader batch_size = 64 train_dataset = CreditDataset(X_train, y_train) val_dataset = CreditDataset(X_val, y_val) test_dataset = CreditDataset(X_test, y_test) train_loader = DataLoader(train_dataset, batch_size=batch_size, shuffle=True) val_loader = DataLoader(val_dataset, batch_size=batch_size) test_loader = DataLoader(test_dataset, batch_size=batch_size) # 初始化模型 input_dim = X_train.shape[1] model = CreditNN(input_dim) print(model) # 损失函数和优化器 criterion = nn.BCELoss() optimizer = optim.Adam(model.parameters(), lr=0.001) # 训练 train_losses, val_losses, train_accs, val_accs = train_model( model, train_loader, val_loader, criterion, optimizer, num_epochs=100, patience=10 ) # 绘制训练历史 plt.figure(figsize=(12, 5)) plt.subplot(1, 2, 1) plt.plot(train_losses, label='Train Loss') plt.plot(val_losses, label='Val Loss') plt.title('Loss Curve') plt.legend() plt.subplot(1, 2, 2) plt.plot(train_accs, label='Train Acc') plt.plot(val_accs, label='Val Acc') plt.title('Accuracy Curve') plt.legend() plt.savefig('training_history.png') print("Saved training_history.png") # 评估 evaluate_model(model, test_loader, feature_names)

结果如下：