R help - Nov 2011 - Reclassify string values

Hi All,

Is there a simple way to convert a string such as c("A", "B"
,"C", "D")
to a string of c("Group1", "Group1", "Group2",
"Group2"). Naturally I
could use the factor function as below but I don't like seeing that 
warning message (and I don't want to turn off warning messages). Perhaps 
a function called "reclassify" or "recategorize"?

Zev

x<-LETTERS[1:4]
x2<-as.character(factor(x, levels=LETTERS[1:4],
labels=rep(c("Group1",
"Group2"), each=2)))

Warning message:
In `levels<-`(`*tmp*`, value = c("Group1", "Group1",
"Group2", "Group2" :
   duplicated levels will not be allowed in factors anymore


-- 
Zev Ross
ZevRoss Spatial Analysis
120 N Aurora, Suite 3A
Ithaca, NY 14850
607-277-0004 (phone)
866-877-3690 (fax, toll-free)
zev at zevross.com

On Thu, Nov 3, 2011 at 11:59 AM, Zev Ross <zev at zevross.com>
wrote:
> Hi All,
>
> Is there a simple way to convert a string such as c("A",
"B" ,"C", "D") to a
> string of c("Group1", "Group1", "Group2",
"Group2"). Naturally I could use
> the factor function as below but I don't like seeing that warning
message
> (and I don't want to turn off warning messages). Perhaps a function
called
> "reclassify" or "recategorize"?
>
> Zev
>
> x<-LETTERS[1:4]
> x2<-as.character(factor(x, levels=LETTERS[1:4],
labels=rep(c("Group1",
> "Group2"), each=2)))
>
> Warning message:
> In `levels<-`(`*tmp*`, value = c("Group1", "Group1",
"Group2", "Group2" :
> ?duplicated levels will not be allowed in factors anymore
If you want to "translate", why not first build a translation table

tt = cbind(LETTERS[1:4], c("group1", "group1",
"group2", "group2"))

then apply it on an example:

xx = sample(LETTERS[1:4], 20, replace = TRUE)

translation = tt[ match(xx, tt[, 1]), 2]
> translation
 [1] "group2" "group2" "group2" "group2"
"group2" "group1" "group2" "group1"
 [9] "group2" "group1" "group1" "group2"
"group2" "group2" "group1" "group2"
[17] "group2" "group1" "group1" "group2"

Or did I misunderstand your intent?

Peter