A characteristic feature of functional data is the presence of time
variability in addition to amplitude variability. The existing functional
regression methods do not handle time variability in an explicit and efficient
way. In this paper we introduce a functional regression method that
incorporates time warping as an intrinsic part of the model. The method
achieves good predictive power in a parsimonious way, and allows for unified
statistical inference of time and amplitude variability.
A characteristic feature of samples of curves is the presence of time
variability in addition to amplitude variability. The existing functional
regression methods do not handle time variability in an efficient manner. We
propose in this paper a regression method that incorporates time warping as an
intrinsic part of the model. In this way, the method attains a high predictive
power in a parsimonious and efficient manner, avoiding overfitting and
simplifying statistical inference.
Outlying curves often occur in functional or longitudinal datasets, and can
be very influential on parameter estimators and very hard to detect visually.
In this article we introduce estimators of the mean and the principal
components that are resistant to, and then can be used for detection of,
outlying sample trajectories.
This article introduces trimmed estimators for the mean and covariance
functional of data in general Hilbert spaces. The estimators are based on a
data depth measure that can be computed on any Hilbert space, because it is
defined only in terms of the interdistances between data points. We show that
the estimators can attain the maximum breakdown point by properly choosing the
tuning parameters, and that they possess better outlier resistance properties
than alternative estimators, as shown by a comparative Monte Carlo study.