* @param groups the groups.
	 * @param maxNumIters the maximum number of iterations.
	 * @param lambda the lambda.
	 * @return a group-lasso penalized regressor.
	 */
	public GLM buildGaussianRegressor(Instances trainSet, List<int[]> groups, int maxNumIters, double lambda) {
		return buildGaussianRegressor(trainSet, isSparse(trainSet), groups, maxNumIters, lambda);
	}