A method for inferring disease similarity by similarity retrieval of electrocardiogram time-series, comprising: acquiring user ECG waveforms correspondingly depicting many cardiac cycles of the heart of many users stored in a database; pre-processing each of the user ECG waveforms through pre-processing steps to isolate sets of single cardiac cycles corresponding to different heart-rates detected for each of the user ECG waveforms, each single cardiac cycle within the many cardiac cycles of the heart of many users corresponds to one single heart-rate detected. acquiring patient ECG waveforms depicting multiple cardiac cycles of the heart of a query patient; pre-processing the patient ECG waveforms through pre-processing steps to isolate sets of single cardiac cycles corresponding to different heart-rates detected for each of the patient ECG waveforms of the query patient, each single cardiac cycle within the multiple cardiac cycles of the heart of the query patient corresponds to one single heart-rate detected.