CODEWITHSUNDEEP
javanullpointerexceptionweka
Nipun Alahakoon
Nipun Alahakoon

Reputation: 2862

Error while evaluating new data on weka java API

When i am trying to evaluate a new testing data on already trained classifier it brings me null point exception.

Here is the code

String[] optionsj = new String[2];

optionsj[0] = "-C";
optionsj[1] = "0.25";

// a decision tree
//Training
Classifier cls = new J48();
cls.setOptions(optionsj);
Evaluation eval = new Evaluation(data);
Random rand = new Random(1);  // using seed = 1
int folds = 10;
eval.crossValidateModel(cls, data, folds, rand);
System.out.println(eval.toSummaryString());     

System.out.println(eval.toClassDetailsString());

//Testing

Evaluation evaltest = new Evaluation(data);
evaltest.evaluateModel(cls, data2);  // line 193
System.out.println(evaltest.toSummaryString());

//data and data2 are two instances of same dataset.

Error i am getting is 

Exception in thread "main" java.lang.NullPointerExceptionat 
at weka.classifiers.trees.J48.distributionForInstance(Unknown Source)
at weka.classifiers.Evaluation.evaluateModelOnceAndRecordPrediction(Unknown Source)
at weka.classifiers.Evaluation.evaluateModel(Unknown Source)
at dentis.Simplified.main(Simplified.java:193)

I cant print the dataset out without a problem. What is this problem? why it occur and how to fix it?

Upvotes: 0

Views: 703

Answers (1)

Sudheera
Sudheera

Reputation: 1947

when you are using evaluateModel you need to build the classifier on the training set first.

cls.buildClassifier(data);

Upvotes: 2

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