dmat {bspline}

Differentiation matrix

Description

Calculate matrix for obtaining coefficients of first-derivative B-spline. They can be calculated as dqw=Md %*% qw. Here, dqw are coefficients of the first derivative, Md is the matrix returned by this function, and qw are the coefficients of differentiated B-spline.

Usage

dmat(nqw = NULL, xk = NULL, n = NULL, f = NULL, same_xk = FALSE)

Arguments

nqw

Integer scalar, row number of qw matrix (i.e. degree of freedom of a B-spline)

xk

Numeric vector, knot positions

n

Integer scalar, B-spline polynomial order

f

Function from which previous parameters can be retrieved. If both f and any of previous parameters are given then explicitly set parameters take precedence over those retrieved from f.

same_xk

Logical scalar, the same meaning as in dbsp

Value

Numeric matrix of size nqw-1 x nqw