On Jan 7, 2010, at 7:31 AM, Ulrich Keller wrote:
I have encountered a strange behaviour of as.integer() which does not
seem correct to me. Sorry if this is just an indication of me not
understanding floating point arithmetic.
.57 * 100
[1] 57
.29 * 100
[1] 29
So far, so good. But:
as.integer(.57 * 100)
[1] 56
as.integer(.29 * 100)
[1] 28
From help page for as.integer:
"Non-integral numeric values are truncated towards zero (i.e.,
as.integer(x) equals trunc(x) there), "
Then again:
all.equal(.57 * 100, as.integer(57))
[1] TRUE
all.equal(.29 * 100, as.integer(29))
[1] TRUE
This behaviour is the same in R 2.10.1 (Ubuntu and Windows) and 2.9.2
(Windows),
all 32 bit versions. Is this really intended?
Yes, it works as documented.
--
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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