| newton.rapheson {elliptic} | R Documentation |
Newton Rapheson iteration to find roots of equations with the emphasis on complex functions
newton.rapheson(initial, f, fdash, maxiter, tol = .Machine$double.eps)
initial |
Starting guess |
f |
Function for which f(z)=0 is to be solved for z |
fdash |
Derivative of function (note: Cauchy-Riemann conditions assumed) |
maxiter |
Maximum number of iterations attempted |
tol |
Tolerance: iteration stops if |f(z)|<tol |
Bog-standard
Returns z with |f(z)|<tol
Robin K. S. Hankin
#Find the two square roots of 2+i:
f <- function(z){z^2-(2+1i)}
fdash <- function(z){2*z}
newton.rapheson( 1.4+0.3i,f,fdash,maxiter=10)
newton.rapheson(-1.4-0.3i,f,fdash,maxiter=10)
#Now find the three cube roots of unity:
g <- function(z){z^3-1}
gdash <- function(z){3*z^2}
newton.rapheson(-0.5+1i,g,gdash,maxiter=10)
newton.rapheson(-0.5-1i,g,gdash,maxiter=10)
newton.rapheson(+0.5+0i,g,gdash,maxiter=10)