diff --git a/Code/Day 34_Random Forests.md b/Code/Day 34_Random Forests.md new file mode 100644 index 0000000..54718e3 --- /dev/null +++ b/Code/Day 34_Random Forests.md @@ -0,0 +1,83 @@ +# 随机森林 + +

+ +

+ +## 导入库 +```Python +import numpy as np +import matplotlib.pyplot as plt +import pandas as pd +``` +## 导入数据集 +```python +dataset = pd.read_csv('Social_Network_Ads.csv') +X = dataset.iloc[:, [2, 3]].values +y = dataset.iloc[:, 4].values +``` +## 将数据集拆分成训练集和测试集 +```python +from sklearn.cross_validation import train_test_split +X_train, X_test, y_train, y_test = train_test_split(X, y, test_size = 0.25, random_state = 0) +``` +## 特征缩放 +```python +from sklearn.preprocessing import StandardScaler +sc = StandardScaler() +X_train = sc.fit_transform(X_train) +X_test = sc.transform(X_test) +``` +### 调试训练集的随机森林 +```python +from sklearn.ensemble import RandomForestClassifier +classifier = RandomForestClassifier(n_estimators = 10, criterion = 'entropy', random_state = 0) +classifier.fit(X_train, y_train) +``` +## 预测测试集结果 +```python +y_pred = classifier.predict(X_test) +``` +## 生成混淆矩阵,也称作误差矩阵 +```python +from sklearn.metrics import confusion_matrix +cm = confusion_matrix(y_test, y_pred) +``` +## 将训练集结果可视化 +```python +from matplotlib.colors import ListedColormap +X_set, y_set = X_train, y_train +X1, X2 = np.meshgrid(np.arange(start = X_set[:, 0].min() - 1, stop = X_set[:, 0].max() + 1, step = 0.01), + np.arange(start = X_set[:, 1].min() - 1, stop = X_set[:, 1].max() + 1, step = 0.01)) +plt.contourf(X1, X2, classifier.predict(np.array([X1.ravel(), X2.ravel()]).T).reshape(X1.shape), + alpha = 0.75, cmap = ListedColormap(('red', 'green'))) +plt.xlim(X1.min(), X1.max()) +plt.ylim(X2.min(), X2.max()) +for i, j in enumerate(np.unique(y_set)): + plt.scatter(X_set[y_set == j, 0], X_set[y_set == j, 1], + c = ListedColormap(('red', 'green'))(i), label = j) +plt.title('Random Forest Classification (Training set)') +plt.xlabel('Age') +plt.ylabel('Estimated Salary') +plt.legend() +plt.show() +``` +## 将测试集结果可视化 +```python +from matplotlib.colors import ListedColormap +X_set, y_set = X_test, y_test +X1, X2 = np.meshgrid(np.arange(start = X_set[:, 0].min() - 1, stop = X_set[:, 0].max() + 1, step = 0.01), + np.arange(start = X_set[:, 1].min() - 1, stop = X_set[:, 1].max() + 1, step = 0.01)) +plt.contourf(X1, X2, classifier.predict(np.array([X1.ravel(), X2.ravel()]).T).reshape(X1.shape), + alpha = 0.75, cmap = ListedColormap(('red', 'green'))) +plt.xlim(X1.min(), X1.max()) +plt.ylim(X2.min(), X2.max()) +for i, j in enumerate(np.unique(y_set)): + plt.scatter(X_set[y_set == j, 0], X_set[y_set == j, 1], + c = ListedColormap(('red', 'green'))(i), label = j) +plt.title('Random Forest Classification (Test set)') +plt.xlabel('Age') +plt.ylabel('Estimated Salary') +plt.legend() +plt.show() +```