R help - Feb 2007 - precision of zero in R

hello,

I have to calculate the determinants of near singular matrices. Presently R just
stop at the precision of  2.16 e-16.

Can some one tell me how can I set the precision of zero in R ?


thanks


chen pu

On 2/3/07, pu chen <pchen at uni-bielefeld.de>
wrote:
> hello,
> I have to calculate the determinants of near singular matrices. Presently R
just stop at the precision of  2.16 e-16.
I'm not sure what you mean by that.  Can you explain how you
determined that number, perhaps including some code?

It happens that on many systems that number is close to the relative
machine precision.  For example, on my version of R
> .Machine$double.eps
[1] 2.220446e-16
> Can some one tell me how can I set the precision of zero in R ?
If you mean how could you change R so that it would give infinitely
precise floating point representations for which the relative machine
precision is zero I think the only answer is "by magic".  In the real
world we need to work with the floating point representations on the
computers that we have access to.  Perhaps you could rethink the
calculation you are attempting to perform.

The Ryacas package can do exact arithmetic:
   http://code.google.com/p/ryacas/
See the vignette for examples.

On 2/3/07, pu chen <pchen at uni-bielefeld.de>
wrote:
> hello,
>
> I have to calculate the determinants of near singular matrices. Presently R
just stop at the precision of  2.16 e-16.
>
> Can some one tell me how can I set the precision of zero in R ?
>
>
> thanks
>
>
> chen pu
>
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