Hi Phil
Try the following
> which(names(iris)=='Species')
[1] 5

HTH
Schalk Heunis

On Mon, Oct 12, 2009 at 8:53 AM, tdm <philb@philbrierley.com> wrote:

>
> Hi,
>
> How do I access the index number of a field given I only know the field
> name?
>
> eg - I want to set the probability of the field 'species' higher than the
> other fields to use in sampling.
>
> > colprob <- array(dim=NCOL(iris))
> > for(i in 1:NCOL(iris)){colprob[i]=0.5}
> > colprob[iris$species] = 1 #this doesn't work
> > colprob
> [1] 0.5 0.5 0.5 0.5 0.5
>
>
>
>
>
> --
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>
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