pracma (version 1.7.9)

newtonInterp: Lagrange and Newtons Interpolation

Description

Lagrange's and Newton's method of polynomial interpolation.

Usage

newtonInterp(x, y, xs = c())
lagrangeInterp(x, y, xs)

Arguments

x, y

x-, y-coordinates of data points defining the polynomial.

xs

either empty, or a vector of points to be interpolated.

Value

• A vector of values at xs of the polynomial defined by x,y.

Details

Straightforward implementation of Lagrange's Newton's method (vectorized in xs).

References

Each textbook on numerical analysis.

See Also

neville, barylag

Examples

p <- Poly(c(1, 2, 3))
fp <- function(x) polyval(p, x)

x <- 0:4; y <- fp(x)
xx <- linspace(0, 4, 51)
yy <- lagrangeInterp(x, y, xx)
yy <- newtonInterp(x, y, xx)
ezplot(fp, 0, 4)
points(xx, yy)