The help page on binary operators (see ?"==") confirms that binary
representation of fractional representation is not catered for and
points to all.equal as a more suitable test method for those cases.
Steve E
>>> Thomas Lumley <[EMAIL PROTECTED]> 13/08/2008 16:47 >>>
Integers (up to a fairly high limit) are represented exactly, as are
fractions whose denominator is a power of two (again up to a fairly high
limit), so x==0 is fine in that sense.
If x is computed by floating point operations you do have to worry
whether these are exact, eg, with
x<-seq(-1,1,length=7)
it is not clear that the fourth element will be exactly zero.
-thomas
On Wed, 13 Aug 2008, Roland Rau wrote:
> Hi,
>
> since many suggestions are following the form of
> x[x==0] (or similar)
> I would like to ask if this is really recommended?
> What I have learned (the hard way) is that one should not test for
equality of
> floating point numbers (which is the default for R's numeric values,
right?)
> since the binary representation of these (decimal) floating point
numbers is
> not necessarily exact (with the classic example of decimal 0.1).
> Is it okay in this case for the value zero where all binary elements
are zero?
> Or does R somehow recognize that it is an integer?
>
> Just some questions out of curiosity.
>
> Thank you,
> Roland
>
>
> rcoder wrote:
>> Hi everyone,
>>
>> I have a matrix that has a combination of zeros and NAs. When I
perform
>> certain calculations on the matrix, the zeros generate "Inf" values.
Is
>> there a way to either convert the zeros in the matrix to NAs, or
only
>> perform the calculations if not zero (i.e. like using something
similar to
>> an !all(is.na() construct)?
>>
>> Thanks,
>>
>> rcoder
>
> ______________________________________________
> R-help@r-project.org mailing list
> 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.
>
Thomas Lumley Assoc. Professor, Biostatistics
[EMAIL PROTECTED] University of Washington, Seattle
______________________________________________
R-help@r-project.org mailing list
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.
*******************************************************************
This email and any attachments are confidential. Any use...{{dropped:8}}
______________________________________________
R-help@r-project.org mailing list
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.
