Issue
EPL
Volume 86, Number 3, May 2009
Article Number 30001
Number of page(s) 5
Section General
DOI http://dx.doi.org/10.1209/0295-5075/86/30001
Published online 12 May 2009
EPL, 86 (2009) 30001
DOI: 10.1209/0295-5075/86/30001

The visibility graph: A new method for estimating the Hurst exponent of fractional Brownian motion

L. Lacasa1, B. Luque1, J. Luque2 and J. C. Nuño3

1   Departamento de Matemática Aplicada y Estadística, ETSI Aeronáuticos, Universidad Politécnica de Madrid Madrid, Spain, EU
2   Departament de Teoria del Senyal i Comunicacions, Universitat Politècnica de Catalunya - Barcelona, Spain, EU
3   Departamento de Matemática Aplicada a los Recursos Naturales, ETSI Montes, Universidad Politécnica de Madrid Madrid, Spain, EU


received 7 January 2009; accepted in final form 14 April 2009; published May 2009
published online 12 May 2009

Abstract
Fractional Brownian motion (fBm) has been used as a theoretical framework to study real-time series appearing in diverse scientific fields. Because of its intrinsic nonstationarity and long-range dependence, its characterization via the Hurst parameter, H, requires sophisticated techniques that often yield ambiguous results. In this work we show that fBm series map into a scale-free visibility graph whose degree distribution is a function of H. Concretely, it is shown that the exponent of the power law degree distribution depends linearly on H. This also applies to fractional Gaussian noises (fGn) and generic $f^{-\beta}$ noises. Taking advantage of these facts, we propose a brand new methodology to quantify long-range dependence in these series. Its reliability is confirmed with extensive numerical simulations and analytical developments. Finally, we illustrate this method quantifying the persistent behavior of human gait dynamics.

PACS
05.45.Tp - Time series analysis.
05.40.Jc - Brownian motion.
89.75.Hc - Networks and genealogical trees.

© EPLA 2009