[Rd] subsetting matrix by subscript=0,x silently skips.
hin-tak.leung at cimr.cam.ac.uk
Thu Jan 18 17:40:38 CET 2007
(I have taken off r-bug@, as multiple e-mails hitting r-bug@ probably
will result in multiple bug reports, knowing most mail server will
Tony Plate wrote:
> The help page for "[" says:
> A third form of indexing is via a numeric matrix with the one column for
> each dimension: each row of the index matrix then selects a single
> element of the array, and the result is a vector. Negative indices are
> not allowed in the index matrix. NA and zero values are allowed: rows of
> an index matrix containing a zero are ignored, whereas rows containing
> an NA produce an NA in the result.
> So, I think it is behaving as documented.
Hmm, fair enough. I guess the NA one make sense (In R as a rule,
NA in, NA out), but I am not sure I understand or agree with
the rationale of silently ignoring (0,x) and (x,0)'s. Any reason for that?
> Hin-Tak Leung wrote:
>> (e-mailing to R-bugs is intentional - the web itnerface seems to
>> be down)
>> > a<- cbind(c(1,2), c(3,4))
>> > a
>> [,1] [,2]
>> [1,] 1 3
>> [2,] 2 4
>> > a[cbind(c(2,2), c(2,1))]
>>  4 2
>> > a[cbind(c(2,3), c(2,1))]
>> Error: subscript out of bounds
>> > a[cbind(c(2,-1), c(2,1))]
>> Error: negative values are not allowed in a matrix subscript
>> > a[cbind(c(2,0), c(2,1))]
>>  4
>> Am somewhat surprised that 2,0 just silently skip over and doesn't
>> throw an error like 2,0 and 2,-1 . Surely it should throw
>> an error about subscript should be >= 1?
>> > sessionInfo()
>> R version 2.4.1 (2006-12-18)
>> attached base packages:
>>  "splines" "stats" "graphics" "grDevices" "utils"
>>  "methods" "base"
>> other attached packages:
>> snpMatrix survival
>> "1.0.4" "2.30"
>> R-devel at r-project.org mailing list
More information about the R-devel