[R] dataframes with only one variable
Prof Brian Ripley
ripley at stats.ox.ac.uk
Thu Jan 12 10:59:11 CET 2006
On Wed, 11 Jan 2006, Erich Neuwirth wrote:
> Subsetting from a dataframe with only one variable
> returns a vector, not a dataframe.
> This seems somewhat inconsistent.
Not at all. It is entirely consistent with matrix-like indexing (the form
> Wouldn't it be better if subsetting would respect
> the structure completely?
It depends how you do it. [sel1,] parallels a matrix, and drops
dimensions unless drop == FALSE is supplied. [sel1] returns a
one-column df, and [[sel1]] returns a vector.
It is just a question of choosing the appropriate tool. And any changes
to this sort of thing (from the White book) would break a lot of careful
>  1 2 3 4
> v1 v2
> 1 1 4
> 2 2 3
> 3 3 2
> 4 4 1
> Erich Neuwirth
> Institute for Scientific Computing and
> Didactic Center for Computer Science
> University of Vienna
> phone: +43-1-4277-39464 fax: +43-1-4277-39459
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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