make_basis: Create linear splines basis

In brokenstick: Broken Stick Model for Irregular Longitudinal Data

Create linear splines basis

Description

This function creates the basis function of a second-order (linear) splines at a user-specific set of break points.

Usage

make_basis(
  x,
  xname = "x",
  internal = NULL,
  boundary = range(x),
  degree = 1L,
  warn = TRUE
)

Arguments

x	numeric vector
xname	predictor name. Default is "x"
internal	a vector of internal knots, excluding boundary knots
boundary	vector of external knots
degree	the degree of the spline. The broken stick model requires linear splines, so the default is degree = 1. Setting degree = 0 yields (crisp) dummy coding, and one column less than for degree = 1.
warn	a logical indicating whether warnings from splines::bs() should be given.

Value

A matrix with length(x) rows and length(breaks) columns, with some extra attributes described by bs().

Note

Before version 0.54, it was standard practice that the knots array always included boundary[1L].

Author(s)

Stef van Buuren 2023

brokenstick documentation built on March 31, 2023, 9:24 p.m.