Fast Fourier Transform (FFT) relies on the HRV frequency-domain analysis techniques. It requires re-sampling of the inherently unevenly sampled heartbeat time-series (RR tachogram) to produce an evenly sampled time series of the heartbeat. However, re-sampling of the heartbeat time — series is found to produce a substantial error when estimating an artificial RR tachogram. DOI:10.48550/arxiv.2208.02234