boostmath (version 1.4.0)

pchip: PCHIP Interpolator

Description

Constructs a PCHIP interpolator given the vectors of abscissas, ordinates, and derivatives.

Usage

pchip(x, y, left_endpoint_derivative = NULL, right_endpoint_derivative = NULL)

Value

An object of class pchip with methods:

• interpolate(xi): Evaluate the interpolator at point xi.

• prime(xi): Evaluate the derivative of the interpolator at point xi.

• push_back(x, y): Add a new control point

Arguments

x

Numeric vector of abscissas (x-coordinates).

y

Numeric vector of ordinates (y-coordinates).

left_endpoint_derivative

Optional numeric value of the derivative at the left endpoint.

right_endpoint_derivative

Optional numeric value of the derivative at the right endpoint.

Examples

x <- c(0, 1, 2, 3)
y <- c(0, 1, 0, 1)
interpolator <- pchip(x, y)
xi <- 0.5
interpolator$interpolate(xi)
interpolator$prime(xi)
interpolator$push_back(4, 1)