Question

Python: Newston-Raphson
I am getting too many iterations and my answer is off in the millions decimal place. Any ideas?

Answer 1

How many is too many?

What level of accuracy do you actually want?

Answer 2

i posted that q by mistake the actual question is how do i use newtons method fr findin roots of a polynomial ?

Answer 3

First u need a guess and the guess must be reasonably close to the actual root.

Answer 4

So let your polynomial be some function of x, f(x) and your initial guess be x_0.

Then x_1 = x_0 - f(x_0) / f ' (x_0) and iterate till u reach a desired accuracy.

Answer 5

tried this

Answer 6

def computeRoot(poly,x_0,epsilon):
count=0
while abs(evaluatePoly(poly,x_0))>epsilon:

x1=x_0-(evaluatePoly(poly,x_0)/computeDeriv(poly,x_0))

x_0=x1
count=count+1

return [x1,count]

Answer 7

print computeRoot([-13.39, 0.0, 17.5, 3.0, 1.0], 0.1, .0001)

Answer 8

heres the error

Traceback (most recent call last):
File "<pyshell#64>", line 1, in <module>
print computeRoot([-13.39, 0.0, 17.5, 3.0, 1.0], 0.1, .0001)
File "<pyshell#63>", line 5, in computeRoot
x1=x_0-(evaluatePoly(poly,x_0)/computeDeriv(poly,x_0))
ZeroDivisionError: float division by zero

Answer 9

Well, if computeDeriv(poly,x_0) (ie the value of the derivative) is zero, you will get this error, no?

Answer 10

What is the polynomial and what is your initial guess?