以下是实现以KNN算法为基分类器的adaBoost算法的Python代码过程:

from sklearn.datasets import load_iris
from sklearn.model_selection import train_test_split
from sklearn.neighbors import KNeighborsClassifier
from sklearn.metrics import accuracy_score
import numpy as np

class AdaBoost:
    def __init__(self, base_classifier, n_estimators):
        self.base_classifier = base_classifier
        self.n_estimators = n_estimators
        self.classifiers = []
        self.alphas = []

    def fit(self, X, y):
        n_samples, n_features = X.shape
        w = np.full(n_samples, 1/n_samples)
        for i in range(self.n_estimators):
            classifier = self.base_classifier.fit(X, y, sample_weight=w)
            y_pred = classifier.predict(X)

            error = np.sum(w * (y_pred != y))
            alpha = 0.5 * np.log((1 - error) / error)

            w *= np.exp(-alpha * y * y_pred)
            w /= np.sum(w)

            self.classifiers.append(classifier)
            self.alphas.append(alpha)

    def predict(self, X):
        y_pred = np.zeros(len(X))
        for classifier, alpha in zip(self.classifiers, self.alphas):
            y_pred += alpha * classifier.predict(X)
        return np.sign(y_pred)

# Load the iris dataset
iris = load_iris()
X, y = iris.data, iris.target

# Split the dataset into training and testing sets
X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.3, random_state=42)

# Initialize the KNN classifier
knn = KNeighborsClassifier(n_neighbors=3)

# Initialize the AdaBoost classifier with KNN as the base classifier
ada_boost = AdaBoost(base_classifier=knn, n_estimators=10)

# Train the AdaBoost classifier
ada_boost.fit(X_train, y_train)

# Predict the labels of the test data using the AdaBoost classifier
y_pred = ada_boost.predict(X_test)

# Calculate the accuracy score of the AdaBoost classifier
accuracy = accuracy_score(y_test, y_pred)
print("Accuracy:", accuracy)

在上面的代码中,我们首先加载了鸢尾花数据集,并将其拆分为训练和测试集。然后,我们初始化了一个KNN分类器,并将其作为基分类器传递给AdaBoost分类器。我们使用AdaBoost的fit方法来训练分类器,并使用predict方法来预测测试数据的标签。最后,我们计算了AdaBoost分类器的准确性,并将其打印出来

实现以KNN算法为基分类器的adaBoost算法请给出实现以及调用输出的python代码过程。

原文地址: https://www.cveoy.top/t/topic/ftts 著作权归作者所有。请勿转载和采集!

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