Learn R Programming

pracma (version 1.8.8)

laguerre: Laguerre's Method

Description

Laguerre's method for finding roots of complex polynomials.

Usage

laguerre(p, x0, nmax = 25, tol = .Machine$double.eps^(1/2))

Arguments

p
real or complex vector representing a polynomial.
x0
real or complex point near the root.
nmax
maximum number of iterations.
tol
absolute tolerance.

Value

  • The root found, or a warning about the number of iterations.

Details

Uses values of the polynomial and its first and second derivative.

References

Fausett, L. V. (2007). Applied Numerical Analysis Using Matlab. Second edition, Prentice Hall.

See Also

roots

Examples

Run this code
# 1 x^5 - 5.4 x^4 + 14.45 x^3 - 32.292 x^2 + 47.25 x - 26.46
p <- c(1.0, -5.4, 14.45, -32.292, 47.25, -26.46)
laguerre(p, 1)   #=> 1.2
laguerre(p, 2)   #=> 2.099987     (should be 2.1)
laguerre(p, 2i)  #=> 0+2.236068i  (+- 2.2361i, i.e sqrt(-5))

Run the code above in your browser using DataLab