[R] ignoring zeros or converting to NA

[Moshe Olshansky]

Since 0 can be represented exactly as a floating point number, there is no problem with something like x[x==0].
What you can not rely on is something like 0.1+0.2 == 0.3 to be TRUE.


--- On Thu, 14/8/08, Roland Rau <roland.rproject at gmail.com> wrote:

> From: Roland Rau <roland.rproject at gmail.com>
> Subject: Re: [R] ignoring zeros or converting to NA
> To: "rcoder" <mpdotbook at gmail.com>
> Cc: r-help at r-project.org
> Received: Thursday, 14 August, 2008, 1:23 AM
> 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
> 
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