Jazzmine Jazzmine - 1 month ago 8
R Question

R use if else logic to assign value to new column

I need to create a new column that is based on one of three possible values found in a column.

These are the rules:

If it has c somewhere in it, the new column should be assigned "third"
If it has b, but not c somewhere in it, the new column should be assigned "second"
If it has a but not b or c somewhere in it, the new column should be assigned "first"


Here's my sample code

x <- c('a,b,c', 'a', 'a,b')

myLetters <- data.frame(x)

setnames(myLetters, "theLetter")

sapply(myLetters$, theLetter, function(x)
if ('c' %in% myLetters$theLetter) {
myLetters$letterStatus <- "third"
} else if ('b' %in% myLetters$theLetter) {
myLetters$letterStatus <- "second"
} else if ('a' %in% myLetters$theLetter) {
myLetters$letterStatus <- "first"
}
)


This is the data I want for each of the rows based upon the sample data for myLetters$letterStatus:

Row 1: third
Row 2: first
Row 3: second


Currently I'm getting "first" "first" "first" but I don't understand why.

Do you know how I can resolve this and why I got first for each row?

Thanks

Answer

using vectorisation (R's gift to us) to obtain the results :

x <- c('a,b,c', 'a', 'a,b')
myLetters <- data.frame(x)
# myLetters
# x
# 1 a,b,c
# 2     a
# 3   a,b

myLetters$x1 = ifelse(grepl("c",myLetters$x), "third", ifelse(grepl("b",myLetters$x),"second", "first"))