Re: [R] R accuracy

[Don MacQueen]

Try
  signif(m,8)
At 1:03 AM -0800 3/23/05, Anthony Landrevie wrote:
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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--
--------------------------------------
Don MacQueen
Environmental Protection Department
Lawrence Livermore National Laboratory
Livermore, CA, USA
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