[R] precision in seq

[Eric Elguero]

Hi everybody,

this is a warning more than a question.

I noticed that seq produces approximate results:

> seq(0,1,0.05)[19]==0.9
[1] TRUE
> seq(0,1,0.05)[20]==0.95
[1] FALSE
> seq(0,1,0.05)[21]==1
[1] TRUE

> seq(0,1,0.05)[20]-0.95
[1] 1.110223024625157e-16

I do not understand why 0.9 and 1 are correct (within some
tolerance or strictly exact?)  and 0.95 is not.

this one works:

> ((0:20)/20)[20]==0.95
[1] TRUE

Eric Elguero