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Curve registration

J. O. Ramsay, Xiaochun Li

Journal of the Royal Statistical Society: Series B (Statistical Methodology) · 1998 · Volume 60 · Issue 2

DOI: 10.1111/1467-9868.00129

Abstract

Functional data analysis involves the extension of familiar statistical procedures such as principal components analysis, linear modelling, and canonical correlation analysis to data where the raw observationxiis a function. An essential preliminary to a functional data analysis is often the registration or alignment of salient curve features by suitable monotone transformationshiof the argumentt, so that the actual analyses are carried out on the valuesxi{hi(t)}. This is referred to as dynamic time warping in the engineering literature. In effect, this conceptualizes variation among functions as being composed of two aspects: horizontal and vertical, or domain and range. A nonparametric function estimation technique is described for identifying the smooth monotone transformationshi, and is illustrated by data analyses. A second-order linear stochastic differential equation is proposed to model these components of variation.

Keywords

Dynamic time warping, Geometric Brownian motion, Monotone functions, Spline, Stochastic time, Time warping

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