[R] table and unique seems to behave differently

[Jeff Newmiller]

I think the question was about table vs unique. Table groups by character representation, unique groups by the underlying representation.

On December 10, 2019 7:03:34 AM PST, Duncan Murdoch <murdoch.duncan using gmail.com> wrote:
>On 10/12/2019 3:53 a.m., Alain Guillet wrote:
>> Hi,
>> 
>> I have a vector (see below the dput) and I use unique on it to get
>unique values. If I then sort the result of the vector obtained by
>unique, I see some elements that look like identical. I suspect it
>could be a matter of rounded values but table gives a different result:
>unlike unique output which contains "3.4  3.4", table has only one cell
>for 3.4.
>> 
>> Can anybody know why I get results that look like incoherent between
>the two functions?
>
>dput() does some rounding, so it doesn't necessarily reproduce values 
>exactly.  For example,
>
>x <- c(3.4, 3.4 + 1e-15)
>unique(x)
>#> [1] 3.4 3.4
>dput(x)
>#> c(3.4, 3.4)
>identical(x, c(3.4, 3.4))
>#> [1] FALSE
>
>If you really want to see exact values, you can use the "hexNumeric" 
>option to dput():
>
>dput(x, control = "hexNumeric")
>#> c(0x1.b333333333333p+1, 0x1.b333333333335p+1)
>identical(x, c(0x1.b333333333333p+1, 0x1.b333333333335p+1))
>#> [1] TRUE
>
>Duncan Murdoch
>
>______________________________________________
>R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide
>http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.

-- 
Sent from my phone. Please excuse my brevity.