Re: [Rd] (PR#12532) Column name disappears when indexing a single column

From: Prof Brian Ripley <ripley_at_stats.ox.ac.uk>
Date: Wed, 13 Aug 2008 07:09:00 +0100 (BST)

On Wed, 13 Aug 2008, cherrera_at_cs.nmsu.edu wrote:

> Good Day,

> I can understand that after indexing a single column in a matrix, R
> will return a vector instead of the single column. However, during the
> conversion to a vector, the column name is lost.

> I was wondering if it would be better to have R return a single column
> matrix (retaining the column name), instead of automatically converting
> to a vector. Users could use as.vector() to convert afterwards.

This is NOT a bug.

You give no example, and your subject line is incorrect. You probably mean 'extracting a single column from a matrix' and no name 'disappears' -- the matrix still has its column names.

I think you have missed the 'drop' argument to matrix indexing, which defaults to TRUE. Maybe it would have been better to have FALSE as the default, but lots of code makes use of it. And you DO have a choice that you seem unaware of. See ?`[`, for example, or any good book on R.

>
> Thanks,
> CMHJ
> <<insert bug report here>>
>
>
>
> --please do not edit the information below--
>
> Version:
> platform = x86_64-unknown-linux-gnu
> arch = x86_64
> os = linux-gnu
> system = x86_64, linux-gnu
> status =
> major = 2
> minor = 7.1
> year = 2008
> month = 06
> day = 23
> svn rev = 45970
> language = R
> version.string = R version 2.7.1 (2008-06-23)
>
> Locale:
> LC_CTYPE=en_US.UTF-8;LC_NUMERIC=C;LC_TIME=en_US.UTF-8;LC_COLLATE=en_US.UTF-8;LC_MONETARY=C;LC_MESSAGES=en_US.UTF-8;LC_PAPER=en_US.UTF-8;LC_NAME=C;LC_ADDRESS=C;LC_TELEPHONE=C;LC_MEASUREMENT=en_US.UTF-8;LC_IDENTIFICATION=C
>
> Search Path:
> .GlobalEnv, package:stats, package:graphics, package:grDevices, package:utils, package:datasets, package:methods, Autoloads, package:base

-- 
Brian D. Ripley,                  ripley_at_stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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