pyNewtonRaphsonQuadratic

# Using Newton-Raphson Iterative Process To Solve A Quadratic Equation

def newton(f,Df,x0,epsilon,max_iter):
    xn = x0
    lastfxn = -9999
    for n in range(0, max_iter):

        # fxn = f(xn)               # <<== I could not get these function calls to be accepted. See next line.
        fxn = xn ** 2 - xn - 6

        # Uncomment the next line to get a trace of the progress of the algorithm
        print("Iteration #", n + 1, "  xn=", xn, "  fxn=", fxn, "  last=", lastfxn)

        # if abs(fxn) < epsilon:                 # <<== this is wrong, see next line
        if abs(fxn - lastfxn) < epsilon:
            print('Found solution after', n + 1, 'iterations.')
            return xn
        lastfxn = fxn               # Remember the latest result obtained, so we can compare with next iteration

        # Dfxn = Df(xn)             # <<== I could not get these function calls to be accepted. See next line.
        Dfxn = 2 * xn - 1

        if Dfxn == 0:
            print('Zero derivative. No solution found.')
            return None
        else:
            xn = xn - fxn / Dfxn

    print('Exceeded maximum iterations. No solution found.')
    return None


# f(xn) = lambda x: x**2 - x - 6
# Df(xn) = lambda x: 2*x - 1
# print (newton(f(xn),Df(xn),1,1e-10,10))       # I could not get those function parameters to work
print(newton("dummy", "dummy", 1, 1e-10, 10))