David G. Márquez

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The application of stochastic differential equations (SDEs) to the analysis of temporal data has attracted increasing attention, due to their ability to describe complex dynamics with physically interpretable equations. In this paper, we introduce a nonparametric method for estimating the drift and diffusion terms of SDEs from a densely observed discrete(More)
One of the most promising non-invasive markers of the activity of the autonomic nervous system is Heart Rate Variability (HRV). HRV analysis toolkits often provide spectral analysis techniques using the Fourier transform, which assumes that the heart rate series is stationary. To overcome this issue, the Short Time Fourier Transform is often used (STFT).(More)
In this paper we address the massive parallelization of the characterization of heartbeats by means of Graphics Processors. Heartbeats are represented with Hermite polynomials due to the compactness and robustness of this representation. Both the off-line and on-line characterization of QRS complexes are covered, thus, assessing the capabilities of Graphics(More)
Population aging places a growing stress on society’s resources. There is a need for Assisted Living (AL) technologies that allow the elderly to live independently as long as possible. The AndroidCare open source project aims to explore what functionality can be provided in a low cost AL solution where no professional health organization is involved in the(More)
When choosing a representation for the classification of heartbeats a common solution is using the coefficients of a linear combination of basis functions, such as Hermite functions. Among the advantages of this representation is the possibility of using model selection criteria for choosing the optimal representation, a property that is missing in other(More)
Nonlinear analysis techniques have been used to study the heart rate variability series (which only contains RR interval information) and the ECG (which contains both RR interval and beat morphology information). It is still an open issue whether the RR series is chaotic or stochastic. Nonlinear properties of ECG are less controversial, despite containing(More)
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