nscpp: Natural Cubic Spline Basis
In trtswitch: Treatment Switching

nscpp

R Documentation

Natural Cubic Spline Basis

Description

Computes the B-spline basis matrix for a natural cubic spline.

Usage

nscpp(
  x = NA_real_,
  df = NA_integer_,
  knots = NA_real_,
  intercept = 0L,
  boundary_knots = NA_real_
)

Arguments

`x`	A numeric vector representing the predictor variable. Missing values are allowed.
`df`	Degrees of freedom, specifying the number of columns in the basis matrix. If `df` is provided, the function selects `df - 1 - intercept` internal knots based on appropriate quantiles of `x`, ignoring any missing values.
`knots`	A numeric vector specifying the internal breakpoints that define the spline. If provided, the number of degrees of freedom will be determined by the length of `knots`.
`intercept`	A logical value indicating whether to include an intercept in the basis. The default is `FALSE`.
`boundary_knots`	A numeric vector of length 2 specifying the boundary points where the natural boundary conditions are applied and the B-spline basis is anchored. If not supplied, the default is the range of non-missing values in `x`.

Value

A matrix with dimensions c(length(x), df), where df is either provided directly or computed as length(knots) + 1 + intercept when knots are supplied. The matrix contains attributes that correspond to the arguments passed to the nscpp function.