[R] factors ordered by mean

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
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| `. `'` 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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