[R] The permutation of one vector into another

[Michael Bedward]

match(b, a) ?

Michael


On 16 September 2010 17:13, Niels Richard Hansen
<Niels.R.Hansen+lists at math.ku.dk> wrote:
> Dear R-help-list
>
> I have two character vectors
>
> a <- c("A", "B", "C")
> b <- c("A", "C", "B")
>
> Then
>
> sapply(a, function(i) grep(i, b))
>
> computes the permutation of the entries in 'b' needed
> to bring 'b' into the same order as 'a'.
>
> I have searched around, but haven't been able to find
> any existing function that compute this permutation.
> Is there such a function doing this -- perhaps more
> efficiently than the above?
>
> For those interested, I need the permutation to bring
> the rows of a data frame into the same order as the
> levels of a factor.
>
> Thanks, Niels
>
> --
> Niels Richard Hansen                     Web:   www.math.ku.dk/~richard
> Associate Professor                      Email: Niels.R.Hansen at math.ku.dk
> Department of Mathematical Sciences             nielsrichardhansen at gmail.com
> University of Copenhagen                 Skype: nielsrichardhansen.dk
> Universitetsparken 5                     Phone: +45 353 20783 (office)
> 2100 Copenhagen Ø                               +45 2859 0765 (mobile)
> Denmark
>
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