Assume we have a dataframe
x y
1 1
2 4
4 5
how can you add a new variable to the dataframe such that if x is less than or equal to 1 it returns "good" if x is between 3 and 5 it returns "bad" else returns "fair"
x y w
1 1 "good"
2 2 "fair"
5 5 "bad"
Applied the method shown by ocram., however this one here does not work.
d1 <- c("e", "c", "a")
d2 <- c("e", "a", "b")
w <- ifelse(d1 == "e" & (d2=="e"), 1, ifelse((d1 == "a") & (d2 =="b"), 2, ifelse(d1 == "e"),3,99))
Any ideas? Thanks
One obvious and straightforward possibility is to use "if-else conditions". In that example
x <- c(1, 2, 4)
y <- c(1, 4, 5)
w <- ifelse(x <= 1, "good", ifelse((x >= 3) & (x <= 5), "bad", "fair"))
data.frame(x, y, w)
** For the additional question in the edit** Is that what you expect ?
> d1 <- c("e", "c", "a")
> d2 <- c("e", "a", "b")
>
> w <- ifelse((d1 == "e") & (d2 == "e"), 1,
+ ifelse((d1=="a") & (d2 == "b"), 2,
+ ifelse((d1 == "e"), 3, 99)))
>
> data.frame(d1, d2, w)
d1 d2 w
1 e e 1
2 c a 99
3 a b 2
If you do not feel comfortable with the ifelse function, you can also work with the if and else statements for such applications.
If you have a very limited number of levels, you could try converting y into factor and change its levels.
> xy <- data.frame(x = c(1, 2, 4), y = c(1, 4, 5))
> xy$w <- as.factor(xy$y)
> levels(xy$w) <- c("good", "fair", "bad")
> xy
x y w
1 1 1 good
2 2 4 fair
3 4 5 bad
Source: Stackoverflow.com