A computer-implemented method for estimating a cardiovascular feature, such as heart interbeat intervals, using time-delay embedding includes receiving a quasiperiodic observational data stream from a biophysiological sensor, selecting a first delay value, and generating a first vector with a first dimensionality in a multidimensional coordinate space from the observational data stream through time-delay embedding. The method also includes selecting a first plane with a second dimensionality equal to one less than the first dimensionality and which passes through an origin of the coordinate space, identifying a plurality of crossings of the first vector through the first plane in one direction, and correlating a time value corresponding to each of the crossings. The method further includes calculating a plurality of periods between the time values corresponding to consecutive crossings, where the periods represent a stream of interbeat intervals.
