Recode a Variable

Combining or rearranging a factor can be tedious if it has many levels. recodeX() supports this step by accepting a direct definition of new levels by enumerating old levelnames as argument and adding an "elseLevel" option. If new levels are given as integer values they will be translated in the according levels.

Usage

recodeX(
  x,
  ...,
  keep = NULL,
  elseLevel = NA,
  ref = NULL,
  useEmpty = FALSE,
  num = FALSE
)

Arguments

x: the factor whose levels are to be altered. If x is character it will be factorized (using factor defaults) but returned as character again.
...: the old levels (combined by c() if there are several) named with the new level:
newlevel_a = c("old_a", "old_b"),
newlevel_b = c("old_c", "old_d")
See examples.
keep: vector of levels that should be left untouched.
elseLevel: the value for levels, which are not matched by newlevel list. If this is set to NULL, the elseLevels will be left unchanged. If set to NA (default) non matched levels will be set to NA.
ref: the reference level, typically a string.
useEmpty: logical. Defines how a new level, which can't be found in x, should be handled. Should it be left in the level's list or be dropped? The default is FALSE, which drops empty levels.
num: logical. If set to TRUE the result will be numeric. This is useful if you want to recode strings to specific numeric values.

Value

the factor having the new levels applied.
if x was a character vector, the result will also be character.

Examples


set.seed(1984)
x <- factor(sample(1:15, 20, replace=TRUE))
levels(x) <- paste("old", levels(x), sep="_")

y <- recodeX(x,
            "new_1"   = c("old_1","old_4","old_5"),
            "new_2"   = c("old_6","old_10","old_11"),
            "new_3"   = c("old_12","old_13"),
            elseLevel = "other")
data.frame(x=x, y=y)
#>         x     y
#> 1   old_8 other
#> 2  old_14 other
#> 3   old_4 new_1
#> 4  old_10 new_2
#> 5   old_1 new_1
#> 6   old_5 new_1
#> 7  old_14 other
#> 8   old_3 other
#> 9  old_15 other
#> 10  old_8 other
#> 11  old_1 new_1
#> 12 old_13 new_3
#> 13  old_4 new_1
#> 14  old_8 other
#> 15  old_1 new_1
#> 16  old_4 new_1
#> 17  old_6 new_2
#> 18 old_15 other
#> 19 old_13 new_3
#> 20 old_13 new_3

# Coding NAs, NA is recoded to new_1
x[5:6] <- NA
x <- x[1:7] 

data.frame(
  x, 
  RecodeNA = recodeX(x,
                    "new_1"   = c("old_4","old_8", NA),
                    elseLevel = "other"),
       
  # NAs remain unaffected, unless specified to be processed      
  NoRecodeNA = recodeX(x,
                      "new_1"   = c("old_4","old_8"),
                      elseLevel = "other")
)         
#>        x RecodeNA NoRecodeNA
#> 1  old_8    new_1      new_1
#> 2 old_14    other      other
#> 3  old_4    new_1      new_1
#> 4 old_10    other      other
#> 5   <NA>    new_1       <NA>
#> 6   <NA>    new_1       <NA>
#> 7 old_14    other      other

# keep some levels, collapse others and reset the reference level
ff <- factor(c("apple","pear","banana","kiwi",
               "mango","peach","grape","plum"))
recodeX(ff, 
       stone=c("peach", "plum"), 
       keep=c("apple","banana"),
       elseLevel = "other", ref="stone")
#> [1] apple  other  banana other  other  stone  other  stone 
#> Levels: stone apple banana other


x <- factor(letters[1:6])

z1 <- recodeX(x, AB=c("a","b"), CD=c("c","d"), elseLevel="none of these")
z2 <- recodeX(x, AB=c("a","b"), CD=c("c","d"), elseLevel=NA)
z3 <- recodeX(x, AB=c("a","b"), CD=c("c","d"), elseLevel=NULL)
z4 <- recodeX(x, AB=c("a","b"), GH=c("g","h"), elseLevel=NA, useEmpty=TRUE)
z5 <- recodeX(x, AB=c("a","b"), GH=c("g","h"), elseLevel=NA, useEmpty=FALSE)

data.frame(z1, z2, z3, z4, z5)
#>              z1   z2 z3   z4   z5
#> 1            AB   AB AB   AB   AB
#> 2            AB   AB AB   AB   AB
#> 3            CD   CD CD <NA> <NA>
#> 4            CD   CD CD <NA> <NA>
#> 5 none of these <NA>  e <NA> <NA>
#> 6 none of these <NA>  f <NA> <NA>

lapply(data.frame(z1, z2, z3, z4, z5), levels)
#> $z1
#> [1] "AB"            "CD"            "none of these"
#> 
#> $z2
#> [1] "AB" "CD"
#> 
#> $z3
#> [1] "AB" "CD" "e"  "f" 
#> 
#> $z4
#> [1] "AB" "GH"
#> 
#> $z5
#> [1] "AB"
#> 

# empty level GH exists in z4...
table(z4, useNA="ifany")
#> z4
#>   AB   GH <NA> 
#>    2    0    4 
# and is dropped in z5
table(z5, useNA="ifany")
#> z5
#>   AB <NA> 
#>    2    4 

# use integers to define the groups to collapse
set.seed(1972)
(likert <- factor(sample(1:10, size=15, replace=TRUE),
                  levels=1:10, labels=gettextf("(%s)", 1:10)))
#>  [1] (4)  (10) (9)  (1)  (3)  (7)  (10) (7)  (8)  (10) (1)  (6)  (9)  (10) (5) 
#> Levels: (1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
recodeX(likert, det=1:6, pas=7:8, pro=9:10)
#>  [1] det pro pro det det pas pro pas pas pro det det pro pro det
#> Levels: det pas pro

# or directly turned to numeric
recodeX(likert, "1"=1:6, "2"=7:8, "5"=9:10, num=TRUE)
#>  [1] 1 5 5 1 1 2 5 2 2 5 1 1 5 5 1

Usage

Arguments

Value

See also

Examples