A nonlinear generalization of the Savitzky-Golay filter and the quantitative analysis of saccades

Weiwei Dai, Ivan Selesnick, John Ross Rizzo, Janet Rucker, Todd Hudson

Research output: Contribution to journalArticlepeer-review

Abstract

The Savitzky-Golay (SG) filter is widely used to smooth and differentiate time series, especially biomedical data. However, time series that exhibit abrupt departures from their typical trends, such as sharp waves or steps, which are of physiological interest, tend to be oversmoothed by the SG filter. Hence, the SG filter tends to systematically underestimate physiological parameters in certain situations. This article proposes a generalization of the SG filter to more accurately track abrupt deviations in time series, leading to more accurate parameter estimates (e.g., peak velocity of saccadic eye movements). The proposed filtering methodology models a time series as the sum of two component time series: a low-frequency time series for which the conventional SG filter is well suited, and a second time series that exhibits instantaneous deviations (e.g., sharp waves, steps, or more generally, discontinuities in a higher order derivative). The generalized SG filter is then applied to the quantitative analysis of saccadic eye movements. It is demonstrated that (a) the conventional SG filter underestimates the peak velocity of saccades, especially those of small amplitude, and (b) the generalized SG filter estimates peak saccadic velocity more accurately than the conventional filter.

Original languageEnglish (US)
Article number10
JournalJournal of vision
Volume17
Issue number9
DOIs
StatePublished - 2017

Keywords

  • Differentiation
  • Quantitative saccade analysis
  • Saccade peak velocity
  • Savitzky-Golay filter
  • Smoothing
  • Sparsity

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems

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