unable to obtain a class label in weka java WEKADUMMYSTRINGFORSTRINGATTRIBUTES*

Question

I am trying to classify an instance in java using the weka library and the tutorials online.

I have built a model in my device and loaded that model from the disk using this code.

public void makeModel() throws Exception
    {
        ArffLoader loader = new ArffLoader();
    loader.setFile(new File("data.arff"));

   Instances structure = loader.getDataSet();
    structure.setClassIndex(1);

// train NaiveBayes

NaiveBayesMultinomial n = new NaiveBayesMultinomial();
FilteredClassifier f = new FilteredClassifier();
StringToWordVector s = new StringToWordVector();

s.setUseStoplist(true);
s.setWordsToKeep(100);

f.setFilter(s);

f.setClassifier(n);
structure.numAttributes();
 f.buildClassifier(structure);
Instance current;


Evaluation eval = new Evaluation(structure);
 eval.crossValidateModel(f, structure, 10, new Random(1));
 System.out.println(eval.toSummaryString("\nResults\n======\n", false));



// output generated model
//System.out.println(f);
 ObjectOutputStream oos = new ObjectOutputStream(
                            new FileOutputStream("classifier.model"));
 oos.writeObject(f);
 oos.flush();
 oos.close();
    }

------------------------ Output-------------

Results

Correctly Classified Instances 20158 79.6948 % Incorrectly Classified Instances 5136 20.3052 % Kappa statistic 0.6737 Mean absolute error 0.0726 Root mean squared error 0.2025 Relative absolute error 38.7564 % Root relative squared error 66.1815 % Coverage of cases (0.95 level) 96.4142 % Mean rel. region size (0.95 level) 27.7531 % Total Number of Instances 25294

Then i used the same model to classify an unlabelled instance.

public void classify() throws Exception
    {
        FilteredClassifier cls = (FilteredClassifier) weka.core.SerializationHelper.read("classifier.model");


Instances unlabeled = new Instances(
                         new BufferedReader(
                           new FileReader("test.arff")));

 // set class attribute
 unlabeled.setClassIndex(0);

 // create copy
 Instances labeled = new Instances(unlabeled);

 // label instances
 for (int i = 0; i < unlabeled.numInstances(); i++) {
     System.out.println(labeled.instance(i).classValue());
     System.out.print(", actual: " + labeled.classAttribute().value((int)labeled.instance(i).classValue()));
   double clsLabel = cls.classifyInstance(unlabeled.instance(i));
   labeled.instance(i).setClassValue(clsLabel);
   System.out.println(", predicted: " + labeled.classAttribute().value((int) clsLabel));
 }
 // save labeled data
System.out.println("ended");


    }

------------------------ Output---------------------------

1.0 , actual: Bud1? is a This is a new new string.txtIlocblobR(?????? @? @? @? @E?DSDB ` @? @? @, predicted: *WEKA*DUMMY*STRING*FOR*STRING*ATTRIBUTES* 2.0 , actual: This is a new new string , predicted: *WEKA*DUMMY*STRING*FOR*STRING*ATTRIBUTES* ended

However, my error is that the predicted is actually *WEKA*DUMMY*STRING*FOR*STRING*ATTRIBUTES* when it should have given me a class label instead.

hkn hkn · Accepted Answer · 2014-05-27T09:41:25

While saving classifier also save Instances (just header, no data required):

Instances instancesSample = new Instances(structure, 0);
instancesSample.setClassIndex(1);
...
ObjectOutputStream oos = new ObjectOutputStream(
                        new FileOutputStream("classifier.model"));
oos.writeObject(f);
oos.writeObject(instancesSample);
oos.flush();
oos.close();

After model is loaded, load saved Instances as instancesSample. While classifying:

ObjectInputStream objectInputStream = new ObjectInputStream(new BufferedInputStream(new FileInputStream("classifier.model")));
FilteredClassifier cls = (FilteredClassifier)= (Classifier) objectInputStream.readObject();
Instances instancesSample = (Instances) objectInputStream.readObject();
objectInputStream.close();

int classIndex = 1;
Instances ins = unlabeled[i];
double clsLabel = cls.classifyInstance(ins);
String prediction = instancesSample.attribute(classIndex).value((int) clsLabel));
System.out.println(", predicted: " + prediction);

unable to obtain a class label in weka java *WEKA*DUMMY*STRING*FOR*STRING*ATTRIBUTES*

Results

2 Answers

unable to obtain a class label in weka java WEKADUMMYSTRINGFORSTRINGATTRIBUTES*