##
## R package splines2 by Wenjie Wang and Jun Yan
## Copyright (C) 2016-2024
##
## This file is part of the R package splines2.
##
## The R package splines2 is free software: You can redistribute it and/or
## modify it under the terms of the GNU General Public License as published by
## the Free Software Foundation, either version 3 of the License, or any later
## version (at your option). See the GNU General Public License at
## <https://www.gnu.org/licenses/> for details.
##
## The R package splines2 is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
##
##' Generalized Bernstein Polynomial Basis Functions
##'
##' Returns generalized Bernstein polynomial basis functions of the given degree
##' over the specified range.
##'
##' The Bernstein polynomial basis functions are defined over the support from 0
##' to 1. The generalized Bernstein polynomial basis functions extend the
##' support to any finite interval in the real line.
##'
##' The function \code{bpoly()} is an alias to encourage the use in a model
##' formula.
##'
##' @name bernsteinPoly
##'
##' @inheritParams bSpline
##'
##' @param x The predictor variable taking values inside of the specified
##' boundary. Missing values are allowed and will be returned as they are.
##' @param integral A logical value. If \code{TRUE}, the integrals of the
##' Bernstein polynomials will be returned. The default value is
##' \code{FALSE}.
##' @param Boundary.knots Boundary points at which to anchor the Bernstein
##' polynomial basis. The default value is \code{NULL} and the boundary
##' knots is set internally to be \code{range(x, na.rm = TRUE)}.
##' @param degree A nonnegative integer representing the degree of the
##' polynomials.
##' @param derivs A nonnegative integer specifying the order of derivatives.
##' The default value is \code{0L} for Bernstein polynomial basis functions.
##'
##' @return A \code{BernsteinPoly} object that is essentially a numeric matrix
##' of dimension \code{length(x)} by \code{degree + as.integer(intercept)}.
##'
##' @example inst/examples/ex-bernsteinPoly.R
##'
##' @export
bernsteinPoly <- function(x, degree = 3, intercept = FALSE,
Boundary.knots = NULL,
derivs = 0L, integral = FALSE,
...)
{
## check inputs
if ((degree <- as.integer(degree)) < 0)
stop("The 'degree' must be a nonnegative integer.")
## take care of possible NA's in `x`
nax <- is.na(x)
if (all(nax)) {
stop("The 'x' cannot be all NA's!")
}
## remove NA's in x
xx <- if (nas <- any(nax)) {
x[! nax]
} else {
x
}
Boundary.knots <- null2num0(Boundary.knots)
## call the engine function
out <- rcpp_bernsteinPoly(
x = xx,
degree = degree,
boundary_knots = Boundary.knots,
complete_basis = intercept,
derivs = derivs,
integral = integral
)
## keep NA's as is
if (nas) {
nmat <- matrix(NA_real_, length(nax), ncol(out))
nmat[! nax, ] <- out
saved_attr <- attributes(out)
saved_attr$dim[1] <- length(nax)
out <- nmat
attributes(out) <- saved_attr
attr(out, "x") <- x
}
## add dimnames for consistency with bs returns
name_x <- names(x)
if (! is.null(name_x)) {
row.names(out) <- name_x
}
## add class
class(out) <- c("BernsteinPoly", "splines2", "matrix")
## return
out
}
##' @rdname bernsteinPoly
##' @export
bpoly <- bernsteinPoly
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