occurence_dict = helper_functions.get_value("ClassOccurences")
occurences = np.array([occurrence for occurrence in occurence_dict.itervalues()],
dtype=np.float64)
return (occurences / y.size).std()
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Reif, A Comprehensive Dataset for Evaluating Approaches of various Meta-Learning Tasks
// defines these five metafeatures as simple metafeatures, but they could also