1st Example

S <- data.frame(SPECIES = c("ORC", "HOBBIT", "ELF", "TROLL", "ORC", "ORC", "ELF", "HOBBIT"), HEIGHT
= c(194, 127, 178, 195, 149, 183, 176, 134))

S

Use nested ifelse commands.

to re-code Orcs as 1, Elves as 2, Hobbits as 3, and Trolls as 4

S[,1] <- ifelse(S[,1] == "ORC", 1, ifelse(S[,1] == "ELF", 2, ifelse(S[,1] == "HOBBIT", 3, ifelse(S[,1] == "TROLL", 4, 99))))

S
NA

recode back

to re-code back

S[,1] <- ifelse(S[,1] == "1", "ORC", ifelse(S[,1] == "2", "ELF", ifelse(S[,1] == "3", "HOBBIT", ifelse(S[,1] == "4", "TROLL", 99))))

S
NA

Very Simple Example

gender <- c("MALE","FEMALE","FEMALE","UNKNOWN","MALE")

gender
[1] "MALE"    "FEMALE"  "FEMALE"  "UNKNOWN" "MALE"

re-code males as 1 and females as 2.

ifelse(gender == "MALE", 1, ifelse(gender == "FEMALE", 2, 3))
[1] 1 2 2 3 1

Generate data (array)

A <- data.frame(Gender = c("F", "F", "M", "F", "B", "M", "M"), Height = c(154, 167, 178, 145, 169, 183, 176))

A
NA

recode values to 1 and 2

# Gender variable is located in the first column, or A[ ,1]
A[,1] <- ifelse(A[,1] == "M", 1, ifelse(A[,1] == "F", 2, 99))

A

recode back to male and female

A[,1] <- ifelse(A[,1]  == "1", "M", ifelse(A[,1]  == "2", "F", 3))
A
NA
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