Vectors in Visual Python

[Arthur]

On 9 Feb 2005 02:29:35 -0800, "FLChamp" <ben.champion at gmail.com>
wrote:

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

One bit of confusion is in names.  There was a name space clash early
on.  As things shook out "Visual Python" is ActiveState's Python
developement environment for Visual Studio .Net
http://www.activestate.com/Products/Visual_Python/ 
and the  3d programming environmnet to which you question refers
became " VPython".  Just a point of information.  Certainly no great
confusion in the context of your question, but there could be in other
contexts.
>
>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?

My understanding:

is that VPython "vectors" are in effect flat 3 element Numeric arrays,
and Numeric ararys can be constructed with Float64 specified as the
datatype.  (wonder if that speciufication is a "declaration", and if
so whether that would indicate some conflict between Python's ideology
(Alex's version) and that of its defacto standard numerical processing
library - but I digress) .

Have you tried feeding the VPython the vectors,  arrays declared as
Float64 types.  

May, or may not, get you somewhere.

Art