Ramsay and Li (1998) point out that there are two types of variation. Range variation, where two time points differ at a comparable time point, and domain variation, when two points differ, but they should not have been compared at a fixed time point, but at comparable time points. This can be done by aligning events in the data across time, or at minimums / maximums in time series data. This removes time-variance and enables further analysis, such as statistical parametric mapping (SPM).

Visual representation of a signal, before and after curve registration. The maximum and minimum events are aligned using a time warping function.

When to use: Before PCA or SPM, or to see the range variation while the timing of the event is irrelevant.

• Learn more: Curve registration for biomechanical waveforms, or see the curve registration dialog
• Tutorial: See the Curve Registration section of the SPM tutorial

J. O. Ramsay, Xiaochun Li, Curve Registration, Journal of the Royal Statistical Society Series B: Statistical Methodology, Volume 60, Issue 2, July 1998, Pages 351–363, https://doi.org/10.1111/1467-9868.00129