[R] sub data frame by expression

[Arne.Muller@aventis.com]

Hi,

thanks for your replies regarding the problem to select a sub data frame by
expression. I start getting an understanding on how indexing works in R.

	thanks for your replies,

	Arne

> -----Original Message-----
> From: Prof Brian Ripley [mailto:ripley at stats.ox.ac.uk]
> Sent: 17 October 2003 12:38
> To: Muller, Arne PH/FR
> Cc: r-help at stat.math.ethz.ch
> Subject: Re: [R] sub data frame by expression
> 
> 
> On Fri, 17 Oct 2003 Arne.Muller at aventis.com wrote:
> 
> > I've the following data frame with 54 rows and 4 colums:
> > 
> > > x                  
> >                   Ratio  Dose Time Batch
> > R.010mM.04h.NEW    0.02 010mM  04h   NEW
> > R.010mM.04h.NEW.1  0.07 010mM  04h   NEW
> > ...
> > R.010mM.24h.NEW.2  0.06 010mM  24h   NEW
> > R.010mM.04h.OLD    0.19 010mM  04h   OLD
> > ...
> > R.010mM.04h.OLD.1  0.49 010mM  04h   OLD
> > R.100mM.24h.OLD    0.40 100mM  24h   OLD
> > 
> > I'd like to create a sub data frame containing all rows 
> where Batch == "OLD"
> > and keeping the 4 colums. Assume that I don't know the 
> order of the rows
> > (otherwise I could just do something like x[1:20,]).
> > 
> > I've tried x[x$Batch == 'OLD'] or x[x[,4] == 'OLD'] but it 
> generates errors.
> 
> That subsets columns, not rows. Try x[x$Batch == "OLD",]
> 
> -- 
> 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
> 
>