R help - Feb 2008 - 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 J?nior
|  .''`. UNIMONTES/Depto. Biologia Geral/Lab. de Biologia Computacional
| : :'  : Campus Universit?rio Prof. Darcy Ribeiro, Vila Mauric?ia
| `. `'` CP: 126, CEP: 39401-089, Montes Claros - MG - Brasil
|   `- Fone: (38) 3229-8187 | ronaldo.reis em unimontes.br | chrysopa em
gmail.com
| http://www.ppgcb.unimontes.br/ | ICQ#: 5692561 | LinuxUser#: 205366

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 J?nior
> |  .''`. UNIMONTES/Depto. Biologia Geral/Lab. de Biologia
Computacional
> | : :'  : Campus Universit?rio Prof. Darcy Ribeiro, Vila Mauric?ia
> | `. `'` 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
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

-- 
Henrique Dallazuanna
Curitiba-Paran?-Brasil
25? 25' 40" S 49? 16' 22" O

On Wed, Feb 20, 2008 at 6:02 PM, Ronaldo Reis Junior <chrysopa at
gmail.com> wrote:
> 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"
Have a look at ?reorder

Hadley

-- 
http://had.co.nz/