>>>>> "TP" == Tony Plate <tpl...@acm.org>
>>>>> on Wed, 22 Apr 2009 14:37:05 -0600 writes:
TP> is.integer() is one of those functions with a name that can be
confusing
TP> -- it looks at the underlying storage type of its argument (e.g.,
TP> integer, floating point, character, etc.) not at the value stored in
the
TP> argument.
TP> So, the type of behavior you see is this:
>> is.integer(1)
TP> [1] FALSE
>> is.integer(as.integer(1))
TP> [1] TRUE
>> is.integer(as.integer(1) * 1.0)
TP> [1] FALSE
>> is.integer(as.integer(NA))
TP> [1] TRUE
>>
TP> Careful reading of ?is.integer does tell you this, but I wouldn't
accuse
TP> that help page of making such information blatantly obvious to new
users
TP> of R.
TP> To test whether a value is an integer value, you can so something like
this:
>> is.wholenumber <- function(x, tolerance = .Machine$double.eps^0.5)
TP> return(abs(x - round(x)) < tolerance)
>> is.wholenumber(1)
TP> [1] TRUE
>> is.wholenumber(seq(1,5,by=0.5))
TP> [1] TRUE FALSE TRUE FALSE TRUE FALSE TRUE FALSE TRUE
>>
Thank you, Tony.
Somewhat contrary to our (R-core) beliefs that a reference
should be concise and correct, I have now added (an abridged
version of) the is.wholenumber() function to the *examples*
on the help(is.integer) page and a note too.
Let's pretend we hope that this will stop such bug reports
;-)
Martin Maechler
TP> The 'tolerance' part is to allow for minor deviations that might be due
TP> to floating point representation issues, e.g., on my computer 1/49 * 49
TP> does not result in a value that is exactly equal to 1:
>> 1/49 * 49 - 1
TP> [1] -1.110223e-16
>> is.wholenumber(1/49 * 49)
TP> [1] TRUE
>> is.wholenumber(1/49 * 49, tol=0)
TP> [1] FALSE
>>
TP> -- Tony Plate
TP> hzambran.newsgro...@gmail.com wrote:
>> Full_Name: Mauricio
>> Version: 2.9.0 (2009-04-17)
>> OS: i486-pc-linux-gnu
>> Submission from: (NULL) (193.205.203.3)
>>
>>
>> This is a very simple function that seems not to be working, according
to the
>> definition given by '?is.integer'.
>>
>> I checked in the Bug Tracking page at http://bugs.R-project.org/, but I
didn't
>> find any related message.
>>
>> The possible problem is:
>>
>>
>>
>>> is.integer(1)
>>>
>> [1] FALSE
>>
>> and 1 is obviously an integer value.
>>
>>
>> I would really appreciate if you could clarify if this is really a bug
or not.
>>
>> Thanks in advance,
>>
>> Mauricio
>>
>>
>>> version
>>>
>> _
>> platform i486-pc-linux-gnu
>> arch i486
>> os linux-gnu
>> system i486, linux-gnu
>> status
>> major 2
>> minor 9.0
>> year 2009
>> month 04
>> day 17
>> svn rev 48333
>> language R
>> version.string R version 2.9.0 (2009-04-17)
>>
>> ______________________________________________
>> R-devel@r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>
>>
TP> ______________________________________________
TP> R-devel@r-project.org mailing list
TP> https://stat.ethz.ch/mailman/listinfo/r-devel
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