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
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