Question

I am using python with scipy for writing some code to converge Cartesian coordinates to Kepler elements and the other way round.

For converting Cartesian to Kepler I use the following expression:

E = scopt.newton(self.f, self.M, self.df, args=(), tol=10^(-10), maxiter=10000)

with

self.f = lambda x: x-self.e*scipy.sin(x)-self.M
self.df= lambda x: 1-self.e*scipy.cos(x)

When running the entire code I get the error:

RuntimeError: Failed to converge after 10000 iterations, value is 5.25182613825

If I run it for less iterations (50), I get:

RuntimeError: Failed to converge after 50 iterations, value is 5.25182613825

Comparing the two values it obviously converges. Even if I reduce the tolerance to 10^(-2) i still get the same runtime error.

Does anybody knows why this error occurs?

Answer 1

The exponentiation operator in Python is **. Use tol=10**(-10) or 1E-10.

^ is bitwise XOR.