Problem with new API (StatisfiedCrossValidation)

[FaroukY]

It seems there is a problem with the new API in StratisfiedCrossValidation. The following example fails with error:

[ERROR] In file /tmp/src/shogun/src/shogun/evaluation/StratifiedCrossValidationSplitting.cpp line 44: Multiclass or binary labels required for stratified crossvalidation

Example.sg:

#  Cross Validation for Binary Classifier
File f_feats_train = csv_file("../../data/classifier_binary_2d_linear_features_train.dat")
File f_feats_test = csv_file("../../data/classifier_binary_2d_linear_features_test.dat")
File f_labels_train = csv_file("../../data/classifier_binary_2d_linear_labels_train.dat")
File f_labels_test = csv_file("../../data/classifier_binary_2d_linear_labels_test.dat")
Math:init_random(2)

#![create_features]
Features features_train = features(f_feats_train)
Labels labels_train = labels(f_labels_train)
Features features_test = features(f_feats_test)
Labels labels_test = labels(f_labels_test)
#![create_features]

#![create_cross_validation]
StratifiedCrossValidationSplitting splitting_strategy(labels_train, 2)
#![create_cross_validation]

Changing this to the following runs fine:

#  Cross Validation for Binary Classifier
File f_feats_train = csv_file("../../data/classifier_binary_2d_linear_features_train.dat")
File f_feats_test = csv_file("../../data/classifier_binary_2d_linear_features_test.dat")
File f_labels_train = csv_file("../../data/classifier_binary_2d_linear_labels_train.dat")
File f_labels_test = csv_file("../../data/classifier_binary_2d_linear_labels_test.dat")
Math:init_random(2)

#![create_features]
Features features_train = features(f_feats_train)
Labels labels_train = labels(f_labels_train)
BinaryLabels old_API(f_labels_train)
Features features_test = features(f_feats_test)
Labels labels_test = labels(f_labels_test)
#![create_features]

#![create_cross_validation]
StratifiedCrossValidationSplitting splitting_strategy(old_API, 2)
#![create_cross_validation]

[karlnapf]

Yep, that is to be expected. You will need to use the conversion methods in there for now.
See #4297 for example