[R] column extraction by name ?

[Prof Brian Ripley]

?match
?pmatch

On Wed, 12 Nov 2003 ryszard.czerminski at pharma.novartis.com wrote:

> I have a data frame (df) with colums x, y and z.
> e.g.  df <- data.frame(x = sample(4), y = sample(4), z = sample(4))
> I can extract column z by: df$z or df[3]
> I can also extract columns x,y by: df[1:2] or by df[-3].
> 
> Is it possible to extract x,y columns in a "symbolic" fashion i.e.
> by equivalent of df[-z] (which is illegal) ???

df[-match("z", names(df))]

df[!(names(df) %in% "z")]

etc

-- 
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