bscpp: B-Spline Basis for Polynomial Splines
In trtswitch: Treatment Switching

bscpp

R Documentation

B-Spline Basis for Polynomial Splines

Description

Computes the B-spline basis matrix for a given polynomial spline.

Usage

bscpp(
  x = NA_real_,
  df = NA_integer_,
  knots = NA_real_,
  degree = 3L,
  intercept = 0L,
  boundary_knots = NA_real_,
  warn_outside = 1L
)

Arguments

`x`	A numeric vector representing the predictor variable.
`df`	Degrees of freedom, specifying the number of columns in the basis matrix. If `df` is provided, the function automatically selects `df - degree - 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 not provided, `df` must be specified.
`degree`	An integer specifying the degree of the piecewise polynomial. The default value is `3`, which corresponds to cubic splines.
`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 B-spline basis should be anchored. If not supplied, the default is the range of non-missing values in `x`.
`warn_outside`	A logical value indicating whether a warning should be issued if any values of `x` fall outside the specified boundary knots.

Value

A matrix with dimensions c(length(x), df). If df is provided, the matrix will have df columns. Alternatively, if knots are supplied, the number of columns will be length(knots) + degree + intercept. The matrix contains attributes that correspond to the arguments passed to the bscpp function.