Vectors in Visual Python

[FLChamp]

SOrry if this message is a little confused, it most probably reflects
the state of the author!

I have made a small program that plots the orbit of a planet in visual
python using visual.vector for all values. If i run the program it is
clear that the orbit is non-keplerian as the planets gradually moves
away from the sun. I am pretty sure the orbit should be keplerian so i
guess there must be some source of error in the program.

I am using "from __future__ import division" and the initial conditions
I have are from NASA's horizons system, all values are accuracte to
more than 10 decimal places.

I was wondering if there was a way to specify the type of number used
by visual.vector, for example, when using an array it is possible to
specify the type as float64. If visual.vector was using a smaller
amount of memory to store the number could this be the source of the
error I am finding? If not what else could be the culprit?

I have used a 4th order RK method which I have previously produced
Keplerian orbits with.

I hope I have made some sense here and look forward to any input

Many Thanks

Ben