weka.core.UnassignedDatasetException when creating an unlabeled instance

Question

I trained an IBK classifier with some training data that I created manually as following:

ArrayList atts = new ArrayList();         


        

Answer 1

The problem is with this line:

double classif = ibk.classifyInstance(newInst);

When you try to classify newInst, Weka throws an exception because newInst has no Instances object (i.e., dataset) associated with it - thus it does not know anything about its class attribute.

You should first create a new Instances object similar to the dataRaw, add your unlabeled instance to it, set class index, and only then try classifying it, e.g.:

Instances dataUnlabeled = new Instances("TestInstances", atts, 0);
dataUnlabeled.add(newInst);
dataUnlabeled.setClassIndex(dataUnlabeled.numAttributes() - 1);        
double classif = ibk.classifyInstance(dataUnlabeled.firstInstance());