Correlation optimized warping and dynamic time warping as preprocessing methods for chromatographic data
Article first published online: 16 JUL 2004
Copyright © 2004 John Wiley & Sons, Ltd.
Journal of Chemometrics
Volume 18, Issue 5, pages 231–241, May 2004
How to Cite
Tomasi, G., van den Berg, F. and Andersson, C. (2004), Correlation optimized warping and dynamic time warping as preprocessing methods for chromatographic data. J. Chemometrics, 18: 231–241. doi: 10.1002/cem.859
- Issue published online: 18 AUG 2004
- Article first published online: 16 JUL 2004
- Manuscript Received: 16 MAY 2004
- Manuscript Accepted: 16 APR 2004
- Manuscript Revised: 23 MAR 2004
- retention time shift;
Two different algorithms for time-alignment as a preprocessing step in linear factor models are studied. Correlation optimized warping and dynamic time warping are both presented in the literature as methods that can eliminate shift-related artifacts from measurements by correcting a sample vector towards a reference. In this study both the theoretical properties and the practical implications of using signal warping as preprocessing for chromatographic data are investigated. The connection between the two algorithms is also discussed. The findings are illustrated by means of a case study of principal component analysis on a real data set, including manifest retention time artifacts, of extracts from coffee samples stored under different packaging conditions for varying storage times. We concluded that for the data presented here dynamic time warping with rigid slope constraints and correlation optimized warping are superior to unconstrained dynamic time warping; both considerably simplify interpretation of the factor model results. Unconstrained dynamic time warping was found to be too flexible for this chromatographic data set, resulting in an overcompensation of the observed shifts and suggesting the unsuitability of this preprocessing method for this type of signals. Copyright © 2004 John Wiley & Sons, Ltd.