Add column with values depending on another column to a dataframe

You can nest ifelse stataments. It's very handy when you are making categorical variables out of continuous ones.

data$c4 <- ifelse(data$c2 >= 0 & data$c2 <= 4, 'low',
                  ifelse(data$c2 >=5 & data$c2 <=9, 'medium',
                         ifelse(data$c2 >=10, 'High', 'something else')

df <- read.table(text = "
c1  c2  c3
x   2   z
y   5   f
c   3   r
a   11  z
         ", h = T)

df$c4 <- cut(df$c2, c(-Inf,4,9,Inf), c("low", "medium", "high"))

> df

  c1 c2 c3     c4
1  x  2  z    low
2  y  5  f medium
3  c  3  r    low
4  a 11  z   high