How do I use libsvm in WEKA?

If you run the classifier weka.classifiers.functions.LibSVM and get the libsvm classes not in CLASSPATH! error message, you are missing the libsvm jar archive in your current classpath. The LibSVM classifier is only a wrapper and doesn't need the libsvm classes to compile (uses Reflection). Check out the LibSVM article for details about how to use this classifier.