Achim Zeileis <[EMAIL PROTECTED]> wrote:
R> x <- 406.7 + 1e-20
R> x
[1] 406.7
R> x == 406.7
[1] TRUE
that is
1.) `==' comparisons have a certain tolerance
No, all.equal() supports tolerance, == does not.
Consider
> .Machine$double.eps
[1] 2.220446e-16
That is, the smallest relative difference that can be represented on
my (fairly typical IEEE-conforming) machine is 2 in 10 to the 16th.
1e-20/406.7 is 2.458815e-23, which is a factor of 10 million too small
a relative difference for the hardware to be able to represent. So in
x <- 406.7 + 1e-20
the value of x is identical to 406.7 in every bit.
Instead of using `==' you should use a comparison with a certain
tolerance you can specify...
Such as ?all.equal
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