Test a single instance in Weka

Question

Does weka require the test instances to have the class attribute. I have used a training set arff file to train the classifier. Now I want to test an instance (not from arff fil

Answer 1

To test instances, the instances must have class labels. Even if you provide class labels, when classifying with the built model, Weka does not see the test instance's class labels. Rather after the testing, it matches whether or not its prediction about the test instance's class is correct. If you have labels in training instances (which you must have) and not on the test instances, then you will get an error message something like "the training and testing sets are not compatible." Thank you.