How does one get the support vectors from Weka's version of libSVM

Here is a small snippet of code that let's you accomplish this task. It uses reflection in java.

	// create Model
	LibSVM libsvmModel = new LibSVM();
	libsvmModel.setKernelType(new SelectedTag(LibSVM.KERNELTYPE_LINEAR, LibSVM.TAGS_KERNELTYPE));
	// train classifier
	libsvmModel.buildClassifier(data);
	// extract trained model via reflection, type is libsvm.svm_model
	// see https://github.com/cjlin1/libsvm/blob/master/java/libsvm/svm_model.java
	svm_model model = getModel(libsvmModel);
	// get the indices of the support vectors in the training data
	// Note: this indices start count at 1 insteadof 0
	java.lang.reflect.Field ind = model.getClass().getDeclaredField("sv_indices");
	int len = Array.getLength(ind.get(model));
	System.out.println("Number of support vectors is "+len);
	int[] indices = new int[len];
	System.out.println("Here are the support vectors ...");
	for (int k = 0; k < len; k++)
	{
	indices[k] = (int) Array.get(ind.get(model), k);
	System.out.println(indices[k]);
	}
	// And the getModel function looks like this
	public static <svm_model> svm_model getModel(LibSVM svm) throws IllegalAccessException, NoSuchFieldException
	{
	java.lang.reflect.Field modelField = svm.getClass().getDeclaredField("m_Model");
	modelField.setAccessible(true);
	//modelField.get(svm).getClass().getDeclaredField("sv_indices");
	return (svm_model) modelField.get(svm);
	}

view raw getSV.java hosted with ❤ by GitHub

Bird watching on a hot summer day

Conception of a nest

Eastern Phoebe

Cardinal

Barn Swallow