说明：  心电信号R波检测的函数，包括降采样，滤波，希尔伯特包络提取三个预处理步骤。其中R波根据阈值检测，相对不应期要根据具体信号适当调整.
(ECG R-wave detection functions, including down-sampling , filtering, Hilbert envelope extracted three pretreatment steps. Wherein R wave detection based on a threshold , the relative refractory period should be adjusted according to the specific signal . )