* @param groups the groups of variables.
	 * @param maxNumIters the maximum number of iterations.
	 * @param numLambdas the number of lambdas.
	 * @param minLambdaRatio the minimum lambda is minLambdaRatio * max lambda.
	 * @return group-lasso penalized classifiers.
	 */
	public List<GLM> buildClassifiers(Instances trainSet, List<int[]> groups, int maxNumIters,
			int numLambdas, double minLambdaRatio) {
		return buildClassifiers(trainSet, isSparse(trainSet), groups, maxNumIters, numLambdas, minLambdaRatio);
	}