[Rd] It's a BUG or a Feature? Generating seq break comparing operators

[R. Michael Weylandt]

R FAQ 7.31

Cheers,
MW

On Thu, Feb 7, 2013 at 10:05 AM, Davide Rambaldi <davide.rambaldi at ieo.eu> wrote:
> Hello everybody:
>
> I get a strange behavior with seq, take a look at this:
>
>> msd <- seq(0.05,0.3, 0.01)
>> msd[13]
> [1] 0.17
>> class(msd)
> [1] "numeric"
>> class(msd[13])
> [1] "numeric"
>> typeof(msd[13])
> [1] "double"
>
> now the problem:
>
>> msd[13] == 0.17
> [1] FALSE
>
> It is strange only to me?
>
> Consider that:
>
>> 0.17 == 0.17
> [1] TRUE
>
> and also
>
>> a <- c(0,1,0.17)
>> a
> [1] 0.00 1.00 0.17
>> a[3] == 0.17
> [1] TRUE
>
> It's a BUG in seq? I suspect something related to doubles …
>
> sessionInfo():
>
> R version 2.15.2 (2012-10-26)
> Platform: x86_64-apple-darwin9.8.0/x86_64 (64-bit)
>
> locale:
> [1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
>
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base
>
> loaded via a namespace (and not attached):
> [1] tools_2.15.2
>
>
> -----------------------------------------------------------
> PLEASE NOTE MY NEW EMAIL ADDRESS
> -----------------------------------------------------------
>
> -----------------------------------------------------
> Davide Rambaldi, PhD.
> -----------------------------------------------------
> IEO ~ MolMed
> [e] davide.rambaldi at ieo.eu
> [e] davide.rambaldi at gmail.com
>
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