[Rd] Re: tail(<matrix>) column numbers

From: Patrick Burns <pburns_at_pburns.seanet.com>
Date: Tue 13 Jul 2004 - 05:27:56 EST

I give it my vote as well.

Pat

Warnes, Gregory R wrote:

>I also vote for the 'helpful' addition on row numbers based on the original
>matrix when no row names are present, with an optional argument to prevent
>this behaviour.
>
>-G
>
>
>
>>-----Original Message-----
>>From: Duncan Murdoch [mailto:dmurdoch@pair.com]
>>Sent: Monday, July 12, 2004 8:06 AM
>>To: Patrick Burns
>>Cc: Martin Maechler; Warnes, Gregory R; Prof Brian Ripley;
>>Kevin Wright;
>>r-devel@stat.math.ethz.ch; Peter Dalgaard
>>Subject: Re: tail(<matrix>) column numbers
>>
>>
>>On Sun, 11 Jul 2004 12:06:44 +0100, Patrick Burns
>><pburns@pburns.seanet.com> wrote :
>>
>>
>>
>>>I disagree with Martin's assertion that "tail" is not useful
>>>for programming. It has a few features relative to the
>>>do-it-yourself approach:
>>>
>>>
>>Me too actually. I think tail() has two uses, interactive and
>>programmatic. I think it would be better for interactive use if
>>the row names were added, and only slightly worse for programmatic use
>>if an option were given to turn them off.
>>
>>In interactive use, I find it unhelpful to be told that something is
>>in row 3 when it's really in row 47.
>>
>>Duncan Murdoch
>>
>>
>>
>>>*) It compactly makes the intention clear.
>>>*) It automatically handles cases where there may be
>>>either a vector or a matrix.
>>>*) It handles cases where there is less data than is being
>>>sought (which may or may not be a good thing).
>>>
>>>"tail" of functions is what is definitely intended for interactive
>>>use.
>>>
>>>Pat
>>>
>>>Martin Maechler wrote:
>>>
>>>
>>>
>>>>>>>>>"PatBurns" == Patrick Burns <pburns@pburns.seanet.com>
>>>>>>>>> on Tue, 27 Jan 2004 14:20:30 +0000 writes:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>[more than half a year ago]
>>>>
>>>> PatBurns> Duncan Murdoch wrote:
>>>>
>>>> .............
>>>>
>>>> DM> One other one I'll look at:
>>>> DM>
>>>> DM> If a matrix doesn't have row names, I might add names
>>>> DM> like '[nn,]' to it, so I get results like
>>>>
>>>> R> x <- matrix(1:100,ncol=2)
>>>> R> tail(x)
>>>> Rout> [,1] [,2]
>>>> Rout> [45,] 45 95
>>>> Rout> [46,] 46 96
>>>> Rout> [47,] 47 97
>>>> Rout> [48,] 48 98
>>>> Rout> [49,] 49 99
>>>> Rout> [50,] 50 100
>>>> Rout>
>>>> DM> instead of the current
>>>>
>>>> R> tail(x)
>>>> Rout> [,1] [,2]
>>>> Rout> [1,] 45 95
>>>> Rout> [2,] 46 96
>>>> Rout> [3,] 47 97
>>>> Rout> [4,] 48 98
>>>> Rout> [5,] 49 99
>>>> Rout> [6,] 50 100
>>>>
>>>> DM> I just want to be careful that this doesn't mess up
>>>> DM> something else.
>>>> DM>
>>>> DM> Duncan Murdoch
>>>>
>>>>
>>>> PatBurns> I think this could be being too "helpful". Using
>>>> PatBurns> tail on a matrix may often be done in a program so
>>>> PatBurns> I think leaving things as they come is the best
>>>> PatBurns> policy.
>>>>
>>>>I tend to disagree, and would like to have us think about it
>>>>again:
>>>>
>>>>1) Duncan's proposal was to only add row names *when*
>>>>
>>>>
>>there are none.
>>
>>
>>>>2) Pat is write that tail() for matrices maybe used not
>>>>
>>>>
>>only interactively
>>
>>
>>>> and help(tail)'s "Value:" section encourages this to
>>>>
>>>>
>>some extent.
>>
>>
>>>> However, how can adding column names to such a
>>>>
>>>>
>>matrix-tail be harmful?
>>
>>
>>>> Well, only in the case where the tail is quite large, the
>>>> added dimnames add unneeded memory and other overhead when
>>>> dealing with that matrix.
>>>>
>>>>But I think, programmers/users caring about efficient code
>>>>wouldn't use tail(<matrix>) in their function code, would they?
>>>>
>>>>In conclusion, I'd still argue for following Duncan's proposal,
>>>>maybe adding a \note{.} to head.Rd stating that these functions
>>>>were meant for interactive use, and for "programming", we'd
>>>>rather recommend the direct (n-k+1):n indexing.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>
>>
>
>
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https://www.stat.math.ethz.ch/mailman/listinfo/r-devel Received on Tue Jul 13 05:38:45 2004

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