using factory methods in kernel ridge regression meta example (#4297)

* using factory methods
* cast labels to regression
* data update

examples/meta/src/regression/kernel_ridge_regression.sg

@@ -1,37 +1,36 @@
-CSVFile f_feats_train("../../data/regression_1d_sinc_features_train.dat")
-CSVFile f_feats_test("../../data/regression_1d_sinc_features_test.dat")
-CSVFile f_labels_train("../../data/regression_1d_sinc_labels_train.dat")
-CSVFile f_labels_test("../../data/regression_1d_sinc_labels_test.dat")
+File f_feats_train = csv_file("../../data/regression_1d_sinc_features_train.dat")
+File f_feats_test = csv_file("../../data/regression_1d_sinc_features_test.dat")
+File f_labels_train = csv_file("../../data/regression_1d_sinc_labels_train.dat")
+File f_labels_test = csv_file("../../data/regression_1d_sinc_labels_test.dat")
 
 #![create_features]
 Features features_train = features(f_feats_train)
 Features features_test = features(f_feats_test)
-RegressionLabels labels_train(f_labels_train)
-RegressionLabels labels_test(f_labels_test)
+Labels labels_train = labels(f_labels_train)
+Labels labels_test = labels(f_labels_test)
 #![create_features]
 
 #![create_appropriate_kernel]
 Kernel k = kernel("GaussianKernel", log_width=0.0)
 #![create_appropriate_kernel]
 
 #![create_instance]
-real tau = 0.001
-KernelRidgeRegression krr(tau, k, labels_train)
+Machine krr = machine("KernelRidgeRegression", labels=labels_train, tau=0.001, kernel=k)
 #![create_instance]
 
 #![train_and_apply]
 krr.train(features_train)
-RegressionLabels labels_predict = krr.apply_regression(features_test)
+Labels labels_predict = krr.apply_regression(features_test)
 #![train_and_apply]
 
 #![extract_alpha]
-RealVector alpha = krr.get_alphas()
+RealVector alphas = krr.get_real_vector("m_alpha")
 #![extract_alpha]
 
 #![evaluate_error]
-MeanSquaredError eval()
+Evaluation eval = evaluation("MeanSquaredError")
 real mse = eval.evaluate(labels_predict, labels_test)
 #![evaluate_error]
 
 # integration testing variables
-RealVector output = labels_test.get_labels()
+RealVector output = labels_test.get_real_vector("labels")

src/shogun/regression/KernelRidgeRegression.cpp

@@ -42,7 +42,7 @@ bool CKernelRidgeRegression::solve_krr_system()
 {
 	SGMatrix<float64_t> kernel_matrix(kernel->get_kernel_matrix());
 	int32_t n = kernel_matrix.num_rows;
-	SGVector<float64_t> y = ((CRegressionLabels*)m_labels)->get_labels();
+	SGVector<float64_t> y = regression_labels(m_labels)->get_labels();
 
 	for(index_t i=0; i<n; i++)
 		kernel_matrix(i,i) += m_tau;
@@ -64,11 +64,7 @@ bool CKernelRidgeRegression::solve_krr_system()
 
 bool CKernelRidgeRegression::train_machine(CFeatures *data)
 {
-	if (!m_labels)
-		SG_ERROR("No labels set\n")
-
-	if (m_labels->get_label_type() != LT_REGRESSION)
-		SG_ERROR("Real labels needed for kernel ridge regression.\n")
+	REQUIRE(m_labels, "No labels set\n")
 
 	if (data)
 	{