Hello,
I am trying to test the precision of R on datasets from The Statistical
Reference Datasets Project http://www.itl.nist.gov/div898/strd/index.html and I
don't manage to understand how R is storing its results.
For example, I calculate a mean on the michelso dataset (100 values) and find:
> m=mean(michel)
> m
V1
299.8524
> print(m,digits=15)
V1
299.8524
> print(m,digits=22)
V1
299.85239999999993
The certified value of the mean is 299.85240, so I try
> print(m-299.8524)
V1
-5.684342e-14
> print(m-299.8524,digits=15)
V1
-5.68434188608080e-14
Does it have a sens to print with more than 15 signifiant digits?
Why is the difference not equal to zero?
I am using R 2.0.1 under Windows XP.
Regards,
Anthony Landrevie
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