Change 3 rows which have the smallest value among all values in R

I have a data that looks like this

What I want is to change the y value of 3 individuals with the lowest x value from f to t so my data would look like this:

|  x  |  y  |
|:---:|:---:|
|  3  |  t  |
|  14 |  f  |
|  1  |  t  |
|  7  |  t  |

Kind regards

>Solution :

You could do this as a one-liner in base R:

within(df, y <- ifelse(rank(x) < 4, "t", "f"))
#>    x y
#> 1  3 t
#> 2 14 f
#> 3  1 t
#> 4  7 t

Data taken from question

df <- data.frame(x = c(3, 14, 1, 7), y = "f")