The L2 norm of a kernel
Computes the L2 norm of a kernel implemented in FKSUM, based on its coefficients. NB: the coefficients will first be normalised so that the kernel represents a density function. Equivalent to sqrt(roughness_K())
numeric vector of positive coefficients.
positive numeric representing the L2 norm of the kernel with coefficients beta/norm_const(beta).
Hofmeyr, D.P. (2019) "Fast exact evaluation of univariate kernel sums", IEEE Transactions on Pattern Analysis and Machine Intelligence, in press.