# How to create a new variable in a data.frame based on a condition?

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"
```

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