ok ok, I will RTFM :-)

In fact:

> msd[13] - 0.17
[1] -2.775558e-17

and of course: 

> all.equal(msd[13],0.17)
[1] TRUE

it a precision problem :-)

Sorry to bother you with this… 

anyway should be FAQ 0.0.

Davide


On Feb 7, 2013, at 11:20 AM, Jari Oksanen wrote:

> This should be FAQ 0.0. No other thing is asked as frequently as this. This is the FAQest of all FAQs, and a mother of all FAQs. At least this should be in R posting guide: "Read FAQ 7.31 before posting!"
> 
> Cheers, Jari Oksanen
> 
> On 07/02/2013, at 12:13 PM, R. Michael Weylandt wrote:
> 
>> R FAQ 7.31
>> 
>> Cheers,
>> MW
>> 
>> On Thu, Feb 7, 2013 at 10:05 AM, Davide Rambaldi <davide.rambaldi@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@ieo.eu
>>> [e] davide.rambaldi@gmail.com
>>> 
>>> ______________________________________________
>>> R-devel@r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-devel
>> 
>> ______________________________________________
>> R-devel@r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
> 
> -- 
> Jari Oksanen, Dept Biology, Univ Oulu, 90014 Finland
> jari.oksanen@oulu.fi, Ph. +358 400 408593, http://cc.oulu.fi/~jarioksa
> 
> 
> 


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