Recode factors

I know this comes up, but I didn't see my exact issue in the archives. I
 have variables in a dataframe that need to be recoded. Here is what I'm
 dealing with

 I have a factor called aa

 > class(aa)

 [1] "factor"

 > table(aa)

 aa
        *    0    1    2    3    A    B    C    D    L    N    T
   0    0 1908  725 2089    0    0   67    0    0    2    1    6

 I need to recode everything that is not a numeric value into a 0. So,
 for example

 > mm <- ifelse(aa == 'B', 0, aa)
 > table(mm)

 mm
   0    3    4    5   11   12   13
  67 1908  725 2089    2    1    6

 The recoding works, but the values are no longer what they were
 previously. For example, what was a '1' is now a '4' etc. Is there a way
 to recode factors and also keep the values the same as they were before?
 That is, a '1' would remain a '1' after the recode?

 After the recoding, I need to convert to a numeric variable. I can do
 this as

 mm <- as.numeric(as.character(aa))

 Harold

 > sessionInfo()

 R version 2.6.2 (2008-02-08)
 i386-pc-mingw32

 locale:
 LC_COLLATE=English_United States.1252;LC_CTYPE=English_United
 States.1252;LC_MONETARY=English_United
 States.1252;LC_NUMERIC=C;LC_TIME=English_United States.1252

 attached base packages:
 [1] stats     graphics  grDevices utils     datasets  methods   base


 other attached packages:
 [1] gdata_2.4.0

 loaded via a namespace (and not attached):
 [1] gtools_2.4.0

 >

-----Original Message-----
From: Henrique Dallazuanna [mailto:wwwhsd at gmail.com] 
Sent: Thursday, March 27, 2008 12:50 PM
To: Doran, Harold
Cc: r-help at r-project.org
Subject: Re: [R] Recode factors

If I understand, you can try this:

levels(x)[is.na(as.numeric(levels(x)))] <- 0

On 27/03/2008, Doran, Harold <HDoran at air.org> wrote:

I know this comes up, but I didn't see my exact issue in 

the archives. 

I  have variables in a dataframe that need to be recoded. 

Here is what 

I'm  dealing with

 I have a factor called aa

 > class(aa)

 [1] "factor"

 > table(aa)

 aa
        *    0    1    2    3    A    B    C    D    L    N    T
   0    0 1908  725 2089    0    0   67    0    0    2    1    6

 I need to recode everything that is not a numeric value 

into a 0. So,  

for example

 > mm <- ifelse(aa == 'B', 0, aa)
 > table(mm)

 mm
   0    3    4    5   11   12   13
  67 1908  725 2089    2    1    6

 The recoding works, but the values are no longer what they were  
previously. For example, what was a '1' is now a '4' etc. 

Is there a 

way  to recode factors and also keep the values the same as 

they were before?

 That is, a '1' would remain a '1' after the recode?

 After the recoding, I need to convert to a numeric 

variable. I can do  

this as

 mm <- as.numeric(as.character(aa))

 Harold

 > sessionInfo()

 R version 2.6.2 (2008-02-08)
 i386-pc-mingw32

 locale:
 LC_COLLATE=English_United States.1252;LC_CTYPE=English_United
 States.1252;LC_MONETARY=English_United
 States.1252;LC_NUMERIC=C;LC_TIME=English_United States.1252

 attached base packages:
 [1] stats     graphics  grDevices utils     datasets  

methods   base

 other attached packages:
 [1] gdata_2.4.0

 loaded via a namespace (and not attached):
 [1] gtools_2.4.0

 >

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