[R] Recoding

[Agustin Lobo]

Thanks. This is a simple and efficient solution
for the case in which the elements of the vector "values"
are integers (which is often the case as in the example that came
to my mind).

Nevertheless, let me suggest having a more
comprehensive function recode in base,
as this is a very usual and well defined
operation.

Agus

Phil Spector wrote:
> Agustin -
>    One way to do it is with named vectors:
> 
>> codes = c(1001,1002,1003)
>> names(codes) = c(1,2,3)
>> values = c(1,1,1,2,3,4,1,10,3)
>> newvalues = codes[values]
>> newvalues
>    1    1    1    2    3 <NA>    1 <NA>    3
> 1001 1001 1001 1002 1003   NA 1001   NA 1003
> 
> Since NAs are placed wherever there wasn't a value in codes,
> those values need to be restored:
> 
>> newvalues[is.na(newvalues)] = values[is.na(newvalues)]
>> newvalues
>    1    1    1    2    3 <NA>    1 <NA>    3
> 1001 1001 1001 1002 1003    4 1001   10 1003
> 
> 
>                                        - Phil Spector
>                      Statistical Computing Facility
>                      Department of Statistics
>                      UC Berkeley
>                      spector at stat.berkeley.edu
> 
> 
> 
> On Fri, 27 Jun 2008, Agustin Lobo wrote:
> 
>> Hi!
>>
>> Given a vector (or a factor within a df),i.e. v1 <- c(1,1,1,2,3,4,1,10,3)
>> and a dictionary
>> cbind(c(1,2,3),c(1001,1002,1003))
>>
>> is there a function (on the same line than recode() in car)
>> to get v2 as c(1001,1001,1001,1002,1003,4,1001,10,1003) ?
>>
>> I'm using myself a function based on match() since
>> long ago (I think that thanks to advice by Prof. B. Ripley),
>> but would like to know if there is an standard function (i.e., like
>> recode()). What I'm using is:
>>
>> "reclas" <- function(v, origen, imagen, directo = T, resto=1)
>> {
>>        if(directo == F) {
>>            aux <- origen
>>                origen <- imagen
>>                imagen <- aux
>>        }
>>        m <- match(v, origen, 0)
>>        #print("match finished")
>>        if(resto==0) v <- v*0
>>        v[m > 0] <- imagen[m]
>>        v
>> }
>>
>> Agus
>>
>> -- 
>> Dr. Agustin Lobo
>> Institut de Ciencies de la Terra "Jaume Almera" (CSIC)
>> LLuis Sole Sabaris s/n
>> 08028 Barcelona
>> Spain
>> Tel. 34 934095410
>> Fax. 34 934110012
>> email: Agustin.Lobo at ija.csic.es
>> http://www.ija.csic.es/gt/obster
>>
>> ______________________________________________
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>> PLEASE do read the posting guide 
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
> 

-- 
Dr. Agustin Lobo
Institut de Ciencies de la Terra "Jaume Almera" (CSIC)
LLuis Sole Sabaris s/n
08028 Barcelona
Spain
Tel. 34 934095410
Fax. 34 934110012
email: Agustin.Lobo at ija.csic.es
http://www.ija.csic.es/gt/obster