CODEWITHSUNDEEP
pythonnumpynewtons-method
Ryan McAree
Ryan McAree

Reputation: 47

How can I adjust this Newton-Raphson for loop to include a range of values for my initial guess so that it prints the number of iterations for each?

I currently have this, I have tried to replace x by defining an 'np.arrange' to do this but keep getting an error that says "only integer scalar arrays can be converted to a scalar index", I think I may need to redefine my function but was hoping there was an easy way to slot in an array to give me a range of values for root and the number of iterations.

import math

#Define Newton-Raphson method as a function using a for loop
def nraphson(fn, dfn, x, tol, maxiter):
    for i in range(maxiter):
        xnew = x - fn(x)/dfn(x)
        if abs(xnew - x) < tol: break
        x = xnew
    return xnew, i

#Define f(x) and f'(x) to be used in Newton-Raphson function
y = lambda x: math.exp(x) - x**2
dy = lambda x: math.exp(x) - 2*x

#Run the Newton-Raphson method with initial x as -1 from estimate
x, n = nraphson(y, dy, -1, 0.0001, 100)
#Printing text allows us to see the value determined for the root
print("the root is %f at %d iterations." % (x,n))

Upvotes: 0

Views: 374

Answers (1)

Seyfi
Seyfi

Reputation: 1980

As in this problem the number of iterations on each cell of input array may be different, then it may better to solve the problem by nested iterations. (nested for loops), I mean a loop iterating over each cell of input over nraphson function.

Upvotes: 1

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