Weka开发[4]-特征选择
特征选择,我对这一部分也不熟,大概讲一下,用AttributeSelection进行特征选择,它需要设置3个方面,第一:对属性评价的类(自己到Weka软件里看一下,英文Attribute Evaluator),第二:搜索的方式(自己到Weka软件里看一下,英文Search Method),第三:就是你要进行特征选择的数据集了。最后调用Filter的静态方法userFilter,感觉写的都是废话,一看代码就明白了。唯一值得一说的也就是别把AttributeSelection的包加错了,代码旁边有注释。
另一个函数懒的解释了(它也不是我写的),基本上是自解释的,不太可能看不懂。
package instanceTest;
import java.io.FileReader;
import java.util.Random;
import weka.attributeSelection.CfsSubsetEval;
import weka.attributeSelection.GreedyStepwise;
import weka.classifiers.Evaluation;
import weka.classifiers.meta.AttributeSelectedClassifier;
import weka.classifiers.trees.J48;
import weka.core.Instances;
import weka.filters.Filter;
import weka.filters.supervised.attribute.AttributeSelection;
public class FilterTest
{
private Instances m_instances = null;
public void getFileInstances( String fileName ) throws Exception
{
FileReader frData = new FileReader( fileName );
m_instances = new Instances( frData );
m_instances.setClassIndex( m_instances.numAttributes() - 1 );
}
public void selectAttUseFilter() throws Exception
{
AttributeSelection filter = new AttributeSelection(); // package weka.filters.supervised.attribute!
CfsSubsetEval eval = new CfsSubsetEval();
GreedyStepwise search = new GreedyStepwise();
filter.setEvaluator(eval);
filter.setSearch(search);
filter.setInputFormat( m_instances );
System.out.println( "number of instance attribute = " +m_instances.numAttributes() );
Instances selectedIns = Filter.useFilter( m_instances, filter);
System.out.println( "number of selected instance attribute = " + selectedIns.numAttributes() );
}
public void selectAttUseMC() throws Exception
{
AttributeSelectedClassifier classifier = newAttributeSelectedClassifier();
CfsSubsetEval eval = new CfsSubsetEval();
GreedyStepwise search = new GreedyStepwise();
J48 base = new J48();
classifier.setClassifier( base );
classifier.setEvaluator( eval );
classifier.setSearch( search );
// 10-fold cross-validation
Evaluation evaluation = new Evaluation( m_instances );
evaluation.crossValidateModel(classifier, m_instances, 10, newRandom(1));
System.out.println( evaluation.toSummaryString() );
}
public static void main( String[] args ) throws Exception
{
FilterTest filter = new FilterTest();
filter.getFileInstances( "F://Program Files//Weka-3-4//data//soybean.arff");
filter.selectAttUseFilter();
filter.selectAttUseMC();
}
}