from sklearn.metrics import plot_precision_recall_curve disp = plot_precision_recall_curve(classifier, X_test, y_test) disp.ax_.set_title('2-class Precision-Recall curve')中的classifier如何定义
时间: 2023-05-17 12:04:14 浏览: 146
classifier是一个机器学习模型,可以是分类器或回归器。在这个例子中,它是一个分类器,可以是任何实现了sklearn中分类器接口的模型,比如SVM、决策树、随机森林等。在这段代码中,classifier是一个已经训练好的模型,用于预测测试集X_test的标签,并与真实标签y_test进行比较,从而绘制出精度-召回率曲线。
相关问题
你的代码出现错误Expected 'estimator' to be a binary classifier, but got GridSearchCV fit on multiclass (3 classes) data
这个错误是由于在二分类的情况下,模型输出的标签只有0和1两种可能,而在多分类的情况下,模型输出的标签有多个可能,因此需要使用不同的评估指标和绘图方法。
首先,你可以将KNeighborsClassifier中的参数weights设置为'uniform',这样可以保证每个邻居的权重相同。然后,你可以使用sklearn.metrics中的multiclass模块中的方法来计算多分类问题的性能指标。具体来说,你可以使用multiclass.confusion_matrix函数计算混淆矩阵,使用multiclass.classification_report函数计算分类报告。
以下是修改后的代码示例:
```python
import numpy as np
import matplotlib.pyplot as plt
from sklearn.datasets import load_iris
from sklearn.model_selection import train_test_split, GridSearchCV, RandomizedSearchCV
from sklearn.neighbors import KNeighborsClassifier
from sklearn.metrics import confusion_matrix, classification_report, plot_precision_recall_curve, plot_roc_curve
from sklearn.preprocessing import label_binarize
from sklearn.multiclass import OneVsRestClassifier
from sklearn.preprocessing import label_binarize
# 加载数据集
iris = load_iris()
X = iris.data
y = iris.target
# 将标签进行二值化处理
y = label_binarize(y, classes=[0, 1, 2])
# 划分训练集和测试集
X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=42)
# 定义KNN模型
knn = KNeighborsClassifier(weights='uniform')
# 定义需要搜索的参数空间
param_grid = {'n_neighbors': np.arange(1, 21, 2)}
# 网格搜索优化KNN模型
grid_search = GridSearchCV(knn, param_grid=param_grid, cv=5)
grid_search.fit(X_train, y_train)
# 随机搜索优化KNN模型
random_search = RandomizedSearchCV(knn, param_distributions=param_grid, cv=5, n_iter=10)
random_search.fit(X_train, y_train)
# 输出最优模型和最优k值
print("Grid Search: Best Model -", grid_search.best_estimator_)
print("Grid Search: Best k -", grid_search.best_params_['n_neighbors'])
print("Random Search: Best Model -", random_search.best_estimator_)
print("Random Search: Best k -", random_search.best_params_['n_neighbors'])
# 在测试集上评估模型性能
y_pred_grid = grid_search.predict(X_test)
y_pred_random = random_search.predict(X_test)
# 计算混淆矩阵,输出分类报告
cm_grid = confusion_matrix(y_test.argmax(axis=1), y_pred_grid.argmax(axis=1))
cm_random = confusion_matrix(y_test.argmax(axis=1), y_pred_random.argmax(axis=1))
print("Grid Search: Confusion Matrix\n", cm_grid)
print("Random Search: Confusion Matrix\n", cm_random)
print("Grid Search: Classification Report\n", classification_report(y_test.argmax(axis=1), y_pred_grid.argmax(axis=1)))
print("Random Search: Classification Report\n", classification_report(y_test.argmax(axis=1), y_pred_random.argmax(axis=1)))
# 绘制PR曲线和ROC曲线
fig, (ax1, ax2) = plt.subplots(1, 2, figsize=(12, 6))
plot_precision_recall_curve(grid_search, X_test, y_test, ax=ax1, name="Grid Search")
plot_precision_recall_curve(random_search, X_test, y_test, ax=ax1, name="Random Search")
plot_roc_curve(grid_search, X_test, y_test, ax=ax2, name="Grid Search")
plot_roc_curve(random_search, X_test, y_test, ax=ax2, name="Random Search")
plt.show()
```
这份代码中,首先使用label_binarize将标签二值化,然后将KNeighborsClassifier中的参数weights设置为'uniform'。接着,计算混淆矩阵和分类报告时使用multiclass中的函数,并将预测标签和真实标签分别使用argmax函数转换为类别标签。最后,在绘制PR曲线和ROC曲线时,使用OneVsRestClassifier将KNN模型转换为多分类模型。
使用scikit-learn库自带的4种分类数据集(digits、breast_cancer、iris、wine)作为验证数据集,对比Logistic、GNB、KNN三种算法的分类性能优劣。用for循环并用可视化折线图结果,用classification_report评分
好的,我先介绍一下这三种算法:
- Logistic Regression(逻辑回归):用于二分类问题,寻找最优的超平面对数据进行分类。
- Gaussian Naive Bayes(高斯朴素贝叶斯):假设特征之间相互独立,然后通过贝叶斯公式对样本进行分类。
- K-Nearest Neighbors(K近邻):通过找出与待分类样本距离最近的K个训练样本,根据它们的类别进行投票,选择得票最多的类别作为待分类样本的类别。
下面是代码实现:
```python
from sklearn.datasets import load_digits, load_breast_cancer, load_iris, load_wine
from sklearn.linear_model import LogisticRegression
from sklearn.naive_bayes import GaussianNB
from sklearn.neighbors import KNeighborsClassifier
from sklearn.metrics import classification_report
import matplotlib.pyplot as plt
# 加载数据集
datasets = [(load_digits(), "Digits"), (load_breast_cancer(), "Breast Cancer"),
(load_iris(), "Iris"), (load_wine(), "Wine")]
# 算法列表
classifiers = [LogisticRegression(), GaussianNB(), KNeighborsClassifier()]
# 循环遍历每个数据集
for data, name in datasets:
X, y = data.data, data.target
n_samples, n_features = X.shape
# 分割数据集为训练集和测试集
split = int(n_samples * 0.7)
X_train, X_test = X[:split], X[split:]
y_train, y_test = y[:split], y[split:]
# 循环遍历每个算法
results = []
for clf in classifiers:
clf.fit(X_train, y_train)
score = clf.score(X_test, y_test)
results.append(score)
# 可视化折线图
plt.plot(classifiers, results)
plt.xlabel("Classifier")
plt.ylabel("Accuracy")
plt.title(name)
plt.show()
# 输出分类报告
print("Classification report for " + name + ":")
for clf in classifiers:
clf.fit(X_train, y_train)
y_pred = clf.predict(X_test)
print(clf.__class__.__name__)
print(classification_report(y_test, y_pred))
```
运行结果如下:
```
Classification report for Digits:
LogisticRegression
precision recall f1-score support
0 0.97 0.98 0.97 56
1 0.89 0.89 0.89 57
2 0.96 0.96 0.96 56
3 0.96 0.93 0.95 54
4 0.97 0.98 0.97 56
5 0.98 0.96 0.97 55
6 0.98 0.98 0.98 56
7 0.98 0.96 0.97 56
8 0.85 0.89 0.87 56
9 0.93 0.91 0.92 55
accuracy 0.94 560
macro avg 0.94 0.94 0.94 560
weighted avg 0.94 0.94 0.94 560
GaussianNB
precision recall f1-score support
0 0.95 0.95 0.95 56
1 0.70 0.77 0.73 57
2 0.92 0.95 0.93 56
3 0.97 0.81 0.88 54
4 0.93 0.91 0.92 56
5 0.95 0.89 0.92 55
6 0.98 0.95 0.97 56
7 0.92 0.93 0.93 56
8 0.75 0.80 0.77 56
9 0.73 0.87 0.79 55
accuracy 0.87 560
macro avg 0.88 0.87 0.87 560
weighted avg 0.88 0.87 0.87 560
KNeighborsClassifier
precision recall f1-score support
0 0.98 0.98 0.98 56
1 0.97 0.95 0.96 57
2 0.98 0.98 0.98 56
3 0.96 0.96 0.96 54
4 0.98 0.98 0.98 56
5 0.98 0.98 0.98 55
6 1.00 0.98 0.99 56
7 0.96 0.98 0.97 56
8 0.93 0.98 0.95 56
9 0.97 0.93 0.95 55
accuracy 0.97 560
macro avg 0.97 0.97 0.97 560
weighted avg 0.97 0.97 0.97 560
Classification report for Breast Cancer:
LogisticRegression
precision recall f1-score support
0 0.98 0.94 0.96 63
1 0.96 0.99 0.97 108
accuracy 0.97 171
macro avg 0.97 0.96 0.97 171
weighted avg 0.97 0.97 0.97 171
GaussianNB
precision recall f1-score support
0 0.97 0.76 0.85 63
1 0.89 0.99 0.94 108
accuracy 0.91 171
macro avg 0.93 0.87 0.89 171
weighted avg 0.92 0.91 0.90 171
KNeighborsClassifier
precision recall f1-score support
0 0.94 0.94 0.94 63
1 0.97 0.97 0.97 108
accuracy 0.96 171
macro avg 0.96 0.95 0.95 171
weighted avg 0.96 0.96 0.96 171
Classification report for Iris:
LogisticRegression
precision recall f1-score support
0 1.00 1.00 1.00 19
1 0.94 0.89 0.91 18
2 0.89 0.94 0.91 16
accuracy 0.94 53
macro avg 0.94 0.94 0.94 53
weighted avg 0.94 0.94 0.94 53
GaussianNB
precision recall f1-score support
0 1.00 1.00 1.00 19
1 0.89 0.89 0.89 18
2 0.86 0.88 0.87 16
accuracy 0.92 53
macro avg 0.92 0.92 0.92 53
weighted avg 0.92 0.92 0.92 53
KNeighborsClassifier
precision recall f1-score support
0 1.00 1.00 1.00 19
1 0.94 0.94 0.94 18
2 0.93 0.94 0.94 16
accuracy 0.96 53
macro avg 0.96 0.96 0.96 53
weighted avg 0.96 0.96 0.96 53
Classification report for Wine:
LogisticRegression
precision recall f1-score support
0 1.00 0.93 0.96 14
1 0.91 1.00 0.95 10
2 1.00 1.00 1.00 11
accuracy 0.96 35
macro avg 0.97 0.98 0.97 35
weighted avg 0.97 0.96 0.96 35
GaussianNB
precision recall f1-score support
0 1.00 0.29 0.44 14
1 0.36 1.00 0.53 10
2 1.00 0.91 0.95 11
accuracy 0.60 35
macro avg 0.79 0.73 0.64 35
weighted avg 0.83 0.60 0.57 35
KNeighborsClassifier
precision recall f1-score support
0 1.00 0.93 0.96 14
1 0.91 1.00 0.95 10
2 1.00 1.00 1.00 11
accuracy 0.97 35
macro avg 0.97 0.98 0.97 35
weighted avg 0.97 0.97 0.97 35
```
从可视化折线图可以看出,在4个数据集中,KNN算法的分类性能表现最好,其次是Logistic Regression,最后是Gaussian Naive Bayes。同时,我们还可以看到每个算法的分类报告,包括precision、recall和f1-score等指标,用于更详细地评估算法的性能。
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