我正在使用adaboost实现一个应用程序,来分类大象是亚洲象还是非洲象。我的输入数据是:
Elephant size: 235 Elephant weight: 3568 Sample weight: 0.1 Elephant type: Asian
Elephant size: 321 Elephant weight: 4789 Sample weight: 0.1 Elephant type: African
Elephant size: 389 Elephant weight: 5689 Sample weight: 0.1 Elephant type: African
Elephant size: 210 Elephant weight: 2700 Sample weight: 0.1 Elephant type: Asian
Elephant size: 270 Elephant weight: 3654 Sample weight: 0.1 Elephant type: Asian
Elephant size: 289 Elephant weight: 3832 Sample weight: 0.1 Elephant type: African
Elephant size: 368 Elephant weight: 5976 Sample weight: 0.1 Elephant type: African
Elephant size: 291 Elephant weight: 4872 Sample weight: 0.1 Elephant type: Asian
Elephant size: 303 Elephant weight: 5132 Sample weight: 0.1 Elephant type: African
Elephant size: 246 Elephant weight: 2221 Sample weight: 0.1 Elephant type: African
我创建了一个分类器类:
import java.util.ArrayList;
public class Classifier {
private String feature;
private int treshold;
private double errorRate;
private double classifierWeight;
public void classify(Elephant elephant){
if(feature.equals("size")){
if(elephant.getSize()>treshold){
elephant.setClassifiedAs(ElephantType.African);
}
else{
elephant.setClassifiedAs(ElephantType.Asian);
}
}
else if(feature.equals("weight")){
if(elephant.getWeight()>treshold){
elephant.setClassifiedAs(ElephantType.African);
}
else{
elephant.setClassifiedAs(ElephantType.Asian);
}
}
}
public void countErrorRate(ArrayList<Elephant> elephants){
double misclassified = 0;
for(int i=0;i<elephants.size();i++){
if(elephants.get(i).getClassifiedAs().equals(elephants.get(i).getType()) == false){
misclassified++;
}
}
this.setErrorRate(misclassified/elephants.size());
}
public void countClassifierWeight(){
this.setClassifierWeight(0.5*Math.log((1.0-errorRate)/errorRate));
}
public Classifier(String feature, int treshold){
setFeature(feature);
setTreshold(treshold);
}
我在main()中训练了一个分类器,它根据“大小”和treshold=250进行分类,就像这样:
main.trainAWeakClassifier("size", 250);
在我的分类器对每头大象进行分类之后,我计算分类器错误,更新每个样本(大象)的权重,并计算分类器的权重。我的问题是:
我如何创建下一个分类器,它如何更关心错误分类的样本(我知道样本权重是关键,但它如何工作,因为我不知道如何实现它)?我是否正确创建了第一个分类器?
1条答案
按热度按时间sr4lhrrt1#
好吧,你可以计算错误率并对示例进行分类,但是你缺少的是对分类器的更新,并根据ada-boost公式将它们组合成一个分类器。看看这里的算法:维基百科的adaboost网页