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

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

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