[R] Integer precision etc.

[Douglas Bates]

(Ted Harding) <Ted.Harding at nessie.mcc.ac.uk> writes:

> With a bit of experimentation I have determined (I think)
> that on my R implementation the largest positive integer
> that is exactly represented is (2^53 - 1), based on
> 
> > (((2^53)-1)+1) - ((2^53)-1)
> [1] 1
> > ((2^53)+1) - (2^53)
> [1] 0

Those "integer" values are being silently converted to double
precision so what you are determining is the relative machine
precision for doubles.  Use .Machine$integer.max instead.  On your
platform it will probably be 2^31-1

> .Machine$integer.max
[1] 2147483647
> log(.Machine$integer.max, 2)
[1] 31
> 2^31-1
[1] 2147483647
> log(.Machine$double.eps, 2)
[1] -52
> log(.Machine$double.neg.eps, 2)
[1] -53