[R] value.labels

[David Winsemius]

On Aug 11, 2011, at 11:42 AM, Uwe Ligges wrote:

>
>
> On 11.08.2011 16:10, zcatav wrote:
>> Hello R people,
>>
>> I have a "data.frame". Status variable has 3 values. 0->alive, 1- 
>> >dead and
>> 2->missed
>> Status as a factor have correct levels. Levels and labels output as  
>> follows;
>>
>> levels(Adbf$status); labels(Adbf$status)
>> [1] "0" "1" "2"
>>   [1] "1"   "2"   "3"   "4"   "5"   "6"   "7"   "8"   "9"   "10"
>>  [11] "11"  "12"  "13"  "14"  "15"  "16"  "17"  "18"  "19"  "20"
>>  [21] "21"  "22"  "23"  "24"  "25"  "26"  "27"  "28"  "29"  "30"
>>  [31] "31"  "32"  "33"  "34"  "35"  "36"  "37"  "38"  "39"  "40"
>>  [41] "41"  "42"  "43"  "44"  "45"  "46"  "47"  "48"  "49"  "50"
>>
>> ........................................................................"644 
>> "
>>
>> Can i add value.labels to status variable? If yes how? Can i see  
>> these
>> value.labels on results or graphics?
>
>
> levels(Adbf$status) <- c("alive", "dead", "missed")

I'm probably making some mistake, but my efforts to use something  
similar to that construction have caused me to "destroy" variables in  
the sense that I have made them all NA's. My more (defensive?,  
unnecessary?)  practice has become:

  Adbf$status <- factor( Adbf$status, labels= c("alive", "dead",  
"missed") )

When I try to use the `levels<-' operation now on what I think is a  
similar object, I get an error but maybe that relates to the fact that  
levels and labels are different?

 > status <- factor( sample(1:50, 400, replace=TRUE)  )
 > status <- status[status %in% c("1", "2", "3")]
 > str(status)
  Factor w/ 50 levels "1","2","3","4",..: 3 3 1 1 2 2 2 2 1 1 ...
 > length(status)
[1] 24
 > levels(status) <- c("alive", "dead", "missed")
Error in `levels<-.factor`(`*tmp*`, value = c("alive", "dead",  
"missed" :
   number of levels differs

The real question I have as a follow-on is what is the "right way" to  
take an object like this:

levels(testres) <- c(levels(testres), "NotDone")
 > testres
[1] 1    2    3    <NA>
Levels: 1 2 3 NotDone

... and add a not done label?

These do not "work":
#1:
 > levels(testres) <- c("NotDone", levels(testres))
 > testres[4]
[1] <NA>
Levels: NotDone 1 2 3

#2:
 > testres <- factor(c(1,2,3,NA))
 > levels(testres) <- c(levels(testres), "NotDone")
 > testres[4]
[1] <NA>
Levels: 1 2 3 NotDone

I have been converting to numeric, changing NA to 0 and then  
refactoring with labels=c("Not done", levels(old_factor) ), but that  
seems B(a)roke.


-- 

David Winsemius, MD
West Hartford, CT