On Tue, 2006-04-25 at 19:16 -0700, Martin Mason wrote:
> Hi Folks,
>
>
>
> Just finishing up a program to convert observations of RA and Dec
> into orbital elements. I am trying to match the precision of my
> measuring instruments, which means I need to worry about how the
> vector object stores its components. I know that the regular float
> variable type has 53 bits of precision. When I display the contents
> of the vector, it seems like it is truncating it to something like 24
> bits. Is this just in the display or is this real? IE
>
> Angular Momentum <0.122495, 0.227241, 1.46103>
> Magnitude of Angular Momentum 1.48366502545
>
>
>
> Is the output just hiding the extra digits or are they disappearing?
> Anyone done any testing on this?
visual.vector stores its components as 3 C "double" variables, which are
equivalent to Python floats. The display is deliberately truncated in
vector.__str__(), but you can provide your own version of that function
that provides the full resolution if you wish.
def my_vector_str(self):
return "<%.15e, %.15e, %.15e>" %(self.x, self.y, self.z)
visual.vector.__str__ = my_vector_str
HTH,
-Jonathan
|
