On 1 Mar 2007 at 12:17, Aimin Yan wrote:
Date sent: Thu, 01 Mar 2007 12:17:09 -0600
To: r-help at stat.math.ethz.ch
From: Aimin Yan <aiminy at iastate.edu>
Subject: [R] number of levels for a factor
> I have temp list which have 19 data.frame
> I want to get number of levels for pr in the first dat.frame
> I do this like this:
> temp[[1]]$pr just has "1A24"
> after I do nlevels(temp[[1]]$pr)
> I expect to get 1, but I get 19
>
> anyone know why?
Hi
help page for [.factor tells you that using subsetting results in
A factor with the same set of levels as x unless drop=TRUE.
I presume your list resulted from some splitting operation and that
original set of levels was preserved.
HTH
Petr
>
> > tail(temp[[1]]$pr)
> [1] 1A24 1A24 1A24 1A24 1A24 1A24
> 19 Levels: 1A24 1A57 1A5J 1A6X 1AB7 1AF8 1AFI 1AGG 1AH9 1AHL 1AJ3 1AJW
> ... 1AZK
> > nlevels(temp[[1]]$pr)
> [1] 19
>
> Aimin
>
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Petr Pikal
petr.pikal at precheza.cz