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。
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
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!