[R] indexing without looping

[David Barron]

One way would be to use merge, like this:

merge(assignation,data.frame(class=x),all.y=TRUE)

There might well be better ways...

On 01/02/07, javier garcia-pintado <jgarcia at ija.csic.es> wrote:
> Hello,
> I've got a data.frame like this:
>
> > > assignation <- data.frame(value=c(6.5,7.5,8.5,12.0),class=c(1,3,5,2))
> > > assignation
> >
>   value class
> 1   6.5     1
> 2   7.5     3
> 3   8.5     5
> 4  12.0     2
>
> > >
> >
>
> and a long vector of classes like this:
>
>
> > > x <- c(1,1,2,7,6,5,4,3,2,2,2...)
> >
>
> And would like to obtain  a vector of length = length(x), with the
> corresponding values extracted from assignation table. Like this:
>
> > > x.value
> >
>  [1]  6.5  6.5 12.0   NA   NA  8.5   NA  7.5 12.0 12.0 12.0
>
> Could you help me with an elegant way to do this ?
> (I just can do it with looping for each class in the assignation table,
> what a think is not perfect in R's sense)
>
> Wishes,
> Javier
>
> --
> Javier García-Pintado
> Institute of Earth Sciences Jaume Almera (CSIC)
> Lluis Sole Sabaris s/n, 08028 Barcelona
> Phone: +34 934095410
> Fax:   +34 934110012
> e-mail:jgarcia at ija.csic.es
>
>
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>
>


-- 
=================================
David Barron
Said Business School
University of Oxford
Park End Street
Oxford OX1 1HP