basefun (version 1.1-4)

polynomial_basis: Polynomial Basis Functions

Description

Basis functions defining a polynomial

Usage

polynomial_basis(var, coef, ui = NULL, ci = NULL)

Arguments

var

a numeric_var object

coef

a logical defining the order of the polynomial

ui

a matrix defining constraints

ci

a vector defining constraints

Details

polynomial_basis returns a function for the evaluation of the basis functions with corresponding model.matrix and predict methods.

Examples

  ### set-up basis of order 3 ommiting the quadratic term
  pb <- polynomial_basis(numeric_var("x", support = c(0, pi)), 
                         coef = c(TRUE, TRUE, FALSE, TRUE))

  ### generate data + coefficients
  x <- as.data.frame(mkgrid(pb, n = 100))
  cf <- c(1, 2, 0, 1.75)

  ### evaluate basis (in two equivalent ways)
  pb(x[1:10,,drop = FALSE])
  model.matrix(pb, data = x[1:10, ,drop = FALSE])

  ### evaluate and plot polynomial defined by
  ### basis and coefficients
  plot(x$x, predict(pb, newdata = x, coef = cf), type = "l")