I'd like to remove any rows where the `value` of `a` >= `b`, but I'm not sure how to do this.

Sample data:

```
df <- data.frame(day = c(1, 1, 2, 2, 3, 3), var = c("a", "b", "a", "b", "a", "b"), value = c(1, 2, 3, 3, 2, 1)

```

Output:

```
  day var value
1   1   a     1
2   1   b     2
3   2   a     3
4   2   b     3
5   3   a     2
6   3   b     1

```

Desired output:

```
  day var value
1   1   a     1
2   1   b     2

```