2

I am getting an error at the following line :

Instance inst =new Instance(1.0, new double[attrs.size()]);

Can any body explain how I can fix this error?

Here is the code:

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import weka.core.Attribute;
import weka.core.FastVector;
import weka.core.Instance;
import weka.core.Instances;
import weka.core.converters.ArffSaver;


public class ContextualFeatureExtractor implements FeatureExtractor{
    private static final int NUMBASEATTR = 1;
    private static final int[] HOURCATEGORY = {3,3,3,3,0,0,0,0,0,0,1,1,1,1,1,1,2,2,2,2,2,2,3,3};
    private static final String[] TIMENAME = {"Morning","Afternoon","Evening","Night"};
    private static final int MINEMOTCOUNT = 100;

    private FastVector attrs;
    private Pattern emotpat;
    private ArrayList<String> emotslist;

    public void setupAttributes(List<Tweet> tweets)
    {
        attrs = new FastVector();
        // Determine attributes

        FastVector hourvals = new FastVector();
        hourvals.addElement(TIMENAME[0]); hourvals.addElement(TIMENAME[1]);
        hourvals.addElement(TIMENAME[2]); hourvals.addElement(TIMENAME[3]);
        Attribute timeofday = new Attribute("TimeOfDay", hourvals);
        attrs.addElement(timeofday);

        // Find frequent emoticons
        emotpat = Pattern.compile("\\p{Graph}*\\p{Punct}\\p{Graph}*");
        HashMap<String,Integer> emots = new HashMap<String,Integer>(100);
        for(Tweet t: tweets)
        {
            Matcher emotmat = emotpat.matcher(t.text);
            while (emotmat.find())
            {
                String curemot = emotmat.group();
                if(curemot.length() > 1 && curemot.length() < 5) {
                    if(emots.containsKey(curemot)) {
                        int curcount = emots.get(curemot);
                        curcount++;
                        emots.put(curemot, curcount);
                    }
                    else
                        emots.put(curemot, 1);
                }
            }
        }
        Set<Map.Entry<String,Integer>> emotset = emots.entrySet();
        Set<String> emotrem = new HashSet<String>(100);
        for(Map.Entry<String,Integer> emotmap : emotset)
        {
            if(emotmap.getValue() < MINEMOTCOUNT)
                emotrem.add(emotmap.getKey());
        }
        Set<String> goodemots = emots.keySet();
        goodemots.removeAll(emotrem);
        emotslist = new ArrayList<String>();
        for(String emot : goodemots)
        {
            Attribute attr = new Attribute("confeature:" + emot);
            attrs.addElement(attr);
            emotslist.add(emot);
        }
    }

    public Instances extractFeatures(List<Tweet> tweets)
    {
        if(attrs == null)
            setupAttributes(tweets);
        Instances feats = new Instances("Contextual Features", attrs, tweets.size());
        feats.setClassIndex(0);
        // Record features

        for(Tweet t: tweets)
        {

            Instance inst =new Instance(1.0, new double[attrs.size()]);
            inst.setDataset(feats);

            int hrcat = HOURCATEGORY[t.hour];
            inst.setValue(0, TIMENAME[hrcat]);

            Matcher emotmat = emotpat.matcher(t.text);
            while (emotmat.find())
            {
                String curemot = emotmat.group();
                if(emotslist.contains(curemot))
                {
                    int attrind = emotslist.indexOf(curemot)+NUMBASEATTR;
                    //double val = inst.value(attrind);
                    //val += 1.0;
                    inst.setValue(attrind, 1.0);
                }

            }           

            feats.add(inst);
        }

         ArffSaver saver = new ArffSaver();
         saver.setInstances(feats);
         try {
            saver.setFile(new File("output/contextual.arff"));
            saver.writeBatch();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return feats;
    }

    public static void main(String[] args) {
        ArrayList<Tweet> tweets = TweetFileParser.parseFile("data/train.40000.2009.05.25");
        ContextualFeatureExtractor cfe = new ContextualFeatureExtractor();
        Instances insts = cfe.extractFeatures(tweets);
        System.out.println(insts.toSummaryString());
    }
}
4

2 回答 2

3

从Javadocs中可以看出它Instance是一个接口——这意味着您不能实例化它，而是必须构造它的一个实现类。（这似乎是BinarySparseInstance或DenseInstance之一SparseInstance。）

然而，我确实看到在其他版本中，Instance是一个具体的类。如果您正在使用库的另一个版本运行一个版本的示例，这可能会导致您遇到此错误。确保您使用的是您期望的版本，并检查该版本的文档以查看您可以调用的内容。

也可以看看：

于 2012-08-14T11:49:10.490 回答
1

weka - LibSVM => libsvm.jar库不在类路径中。从这里下载。或者，如果您有库，则将其添加到您的类路径中。

于 2012-08-14T10:49:34.727 回答