[R] Is k equivalent to k:k ?
Martin Maechler
maechler at stat.math.ethz.ch
Mon Aug 2 17:15:45 CEST 2004
>>>>> "Georgi" == Georgi Boshnakov <georgi.boshnakov at umist.ac.uk>
>>>>> on Mon, 2 Aug 2004 15:46:37 +0100 writes:
Georgi> Hi, I wonder if the following (apparent)
Georgi> inconsistency is a bug or feature.
a feature "of course".
Georgi> Since scalars are simply vectors of length one I
Georgi> would think that a and a:a produce the same result.
Why would you?
Have you read the documentation for ":" carefully?
{Part this topic, namely that a numeric constant such as "4"
is a "double" in R (but integer in S-plus since S+5.0)
should probably finally end up in the R FAQ ...
}
Regards, Martin Maechler
Georgi> For example,
>> identical(4.01,4.01:4.01)
Georgi> [1] TRUE
Georgi> However,
Georgi> identical(4,4:4)
Georgi> [1] FALSE
Georgi> and
>> identical(4.0,4.0:4.0)
Georgi> [1] FALSE
Georgi> A closer look reveals that the colon operator produces objects of different class, e.g.
a closer look wouldn't have been necessary had you read and
understood the documentation.
>> class(4)
Georgi> [1] "numeric"
>> class(4.0)
Georgi> [1] "numeric"
Georgi> but
>> class(4:4)
Georgi> [1] "integer"
>> class(4.0:4.0)
Georgi> [1] "integer"
Georgi> Georgi Boshnakov
Georgi> ------------------------------------------------------------------------------
Georgi> Dr Georgi Boshnakov tel.: +44 (0)161 200 3684
Georgi> Mathematics Department email: georgi.boshnakov at umist.ac.uk
Georgi> UMIST
Georgi> P O Box 88
Georgi> Manchester M60 1QD
Georgi> UK
Georgi> [[alternative HTML version deleted]]
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