[R] factors ordered by mean

[Henrique Dallazuanna]

Try this:
factor(pH,levels=names(sort(tapply(Riqueza,pH,mean))))

2008/2/20, Ronaldo Reis Junior <chrysopa at gmail.com>:
> Hi,
>
> How to order the levels os factor not by alphabetic order but by mean of Y.
> Somethink like this:
>
> I have this alphabetic order:
>
> > levels(pH)
> [1] "alto"  "baixo" "medio"
>
> the order by mean os yvar is:
> > sort(tapply(Riqueza,pH,mean))
>    baixo    medio     alto
> 11.56667 20.00000 26.80000
>
> How to make the levels of pH ordered by this mean to the result to see
> somethink like this:
>
> > levels(pH)
> [1] "baixo"  "medio"  "alto"
>
> I try this to make a function that I need to get ordered levels by this mean
> and after rename to make a automatic contrasts by comparing models.
>
> > levels(pH)[1] <- "baixomedio"
> > levels(pH)[2] <- "baixomedio"
> > levels(pH)
> [1] "baixomedio"  "alto"
>
> and after this a make a new model to be compared with a model with 3 levels
> where "baixo" and "medio" is separated.
>
> without ordered levels these command is wrong because the levels(pH)[1]
> is "alto" and not "baixo".
>
> Normally I use recode from car package, but for automatization your syntax
> is
> a difficult.
>
> Thanks
> Ronaldo
> --
> > Prof. Ronaldo Reis Júnior
> |  .''`. UNIMONTES/Depto. Biologia Geral/Lab. de Biologia Computacional
> | : :'  : Campus Universitário Prof. Darcy Ribeiro, Vila Mauricéia
> | `. `'` CP: 126, CEP: 39401-089, Montes Claros - MG - Brasil
> |   `- Fone: (38) 3229-8187 | ronaldo.reis at unimontes.br | chrysopa at gmail.com
> | http://www.ppgcb.unimontes.br/ | ICQ#: 5692561 | LinuxUser#: 205366
>
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-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O