MaplePrimes - answers and comments on Question, Why isn't the code working properly?

n

Joe Riel — Wed, 28 Oct 2009 22:44:00 Z

What is is 'n' doing there? It is in the snippet ( f(x)^2) n

suggestion

Joe Riel — Wed, 28 Oct 2009 23:18:21 Z

There is no good reason to recompute D(f) and (D@@2)(f) inside the loop. Better to assign them to local variables. You may then notice that there is a problem, no argument is passed to (D@@2)(f). If you also assign some intermediate computations, you can then quickly see where things are going wrong by tracing the procedure call (i.e. call debug(NEWTON_RALPH) before evaluating.

Thank U

Jabz — Thu, 29 Oct 2009 22:14:47 Z

Thanx for ur help Joe and pagan much appriciated.

Newton_Raph

mbendame — Fri, 30 Oct 2009 19:06:57 Z

I had a quick look at the code and it seems that you're trying to evaluate f(x) while f is not a function.

Try the folowing:

f := x -> x^2-5:

NEWTON_RAPH:= proc(z,M)
   local x,A:
   x := z:
   for A to M do:
   x := (x -(f(x)/D(f)(x)) -((((D@@2)(f))*((f(x))^2))/(2*(D(f)(x))^3)))
   end do:
   evalf(x):
end proc:

NEWTON_RAPH(0.1,10);

sign error

Hakan Tiftikci — Sat, 31 Oct 2009 10:36:57 Z

i noticed that there is an error in the sign of third term of x update equation (for higher order Newton iteration): the line x := (x -(f(x)/D(f)(x)) -((((D@@2)(f))*((f(x))^2))/(2*(D(f)(x))^3))) should be x := x -(f(x)/D(f)(x)) + ((((D@@2)(f))*((f(x))^2))/(2*(D(f)(x))^3)); then following modified code finds the solution NEWTON_RAPH:= proc(f,z,M) local x,A; x := z: for A to M do: x := x -(f(x)/D(f)(x)) + ((((D@@2)(f))*((f(x))^2))/(2*(D(f)(x))^3)); end do: evalf(x): proc: f:= x-> x^2-5: NEWTON_RAPH(f,1,10); evalf(%);

Thank u

Jabz — Thu, 12 Nov 2009 09:02:01 Z

Thank u everyone who posted a reply i a,m very grateful 4 ur assistance