Re: [Rd] subsetting matrix by subscript=0,x silently skips.

From: Tony Plate <tplate_at_blackmesacapital.com>
Date: Thu 18 Jan 2007 - 15:44:17 GMT

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.

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))]
> [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))]
> [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)
> i686-redhat-linux-gnu
>
> locale:
> LC_CTYPE=en_GB.UTF-8;LC_NUMERIC=C;LC_TIME=en_GB.UTF-8;LC_COLLATE=en_GB.UTF-8;LC_MONETARY=en_GB.UTF-8;LC_MESSAGES=en_GB.UTF-8;LC_PAPER=en_GB.UTF-8;LC_NAME=C;LC_ADDRESS=C;LC_TELEPHONE=C;LC_MEASUREMENT=en_GB.UTF-8;LC_IDENTIFICATION=C
>
> attached base packages:
> [1] "splines" "stats" "graphics" "grDevices" "utils" "datasets"
> [7] "methods" "base"
>
> other attached packages:
> snpMatrix survival
> "1.0.4" "2.30"
> >
>
> ______________________________________________
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> https://stat.ethz.ch/mailman/listinfo/r-devel
>



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https://stat.ethz.ch/mailman/listinfo/r-devel Received on Fri Jan 19 03:36:27 2007

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