ABSTRACT
Functional data represent data collected in the form of curves, surfaces, images, or anything else varying over a continuum. The continuum can be time, spatial position, wavelength, probability, and so forth. Owing to the emergence of various novel measurement tools, such as eye-trackers, motion capture devices, and functional neuroimaging modalities (e.g., positron emission tomography, functional magnetic resonance imaging, electroencephalography, etc.), functional data become ubiquitous. A few examples of such data collected in psychology or other social sciences include data from motor control (e.g., Mattar and Ostry 2010; Olshen et al. 1989), emotional speech production (Lee, Bresch, and Narayanan 2006), musical cognition (e.g., Almansa and Delicado 2009; Vines et al. 2006; Vines, Nuzzo, and Levitin 2005), gaze-tracking (e.g., Jackson and Sirois 2009), functional neuroimaging (e.g., Hwang et al. 2012a; Tian 2010), online auction (e.g., Jank and Shmueli 2006; Reddy and Dass 2006), and intra-daily stock market (e.g., Alva, Romo, and Ruiz 2009).
