Fig. 5

Performance of k-nearest neighbor models in terms of a area under the receiver operating characteristic curve, b F1-score, and c cross-entropy loss. The horizontal axes represent the sizes of the training samples in percentage. R + L combination and R + E combination, the kNN models that the nearest neighbor out of the randomly selected training samples was determined by the learned similarity and the Euclidean distance, respectively; L + E combination, the kNN model that the nearest neighbor out of the similar training samples based on the learned similarity was determined by the Euclidean distance; E + L combination, the kNN model that the nearest neighbor out of the similar training samples based on the Euclidean distance was determined by the learned similarity