[Solved] Nullpointer exception while using Weka classifier

by


Since you didn’t provide all relevant information, I’ll take a shot in the dark:

I’m assuming that you’re using Weka version 3.7.5 and I found the following source code for Logistic.java online

public double [] distributionForInstance(Instance instance) throws Exception {
    // line 710
    m_ReplaceMissingValues.input(instance);
    instance = m_ReplaceMissingValues.output();
    ...
}

Assuming you didn’t pass null for instance, this only leaves m_ReplaceMissingValues. That member is initialized when the method Logistic.buildClassifier(Instances train)is called:

public void buildClassifier(Instances train) throws Exception {
    ...
    // missing values   
    m_ReplaceMissingValues = new ReplaceMissingValues();
    m_ReplaceMissingValues.setInputFormat(train);
    train = Filter.useFilter(train, m_ReplaceMissingValues);
    ...
}

It looks like you’ve never trained your classifier Logistic on any data after you created the object in the line

Classifier cls = (Classifier) Utils.forName(Classifier.class, classname, tmpOptions);

1

solved Nullpointer exception while using Weka classifier