“…Nonparametric or structure-free methods for curve estimation from functional data involve the concept of density, not least because they generally are based on estimators of Nadaraya-Watson type which require di-vision by an estimator of a small-ball probability. See, for example, Ferraty, Goïa and Vieu (2002a, 2002b, 2007a, 2007b, Ferraty and Vieu (2002, 2003, 2004, 2006a, 2006b and Niang (2002). There is of course a more general and very large methodology for functional data analysis, accessible via the monographs by Silverman (2002, 2005).…”