Suppose I have the following vector:

```
x <- c(8, 6, 9, 9, 7, 3, 2, 5, 5, 1, 6, 8, 5, 2, 9, 3, 5, 10, 8, 2)
```

How can I find which elements are either 8 or 9?

This is one way to do it. First I get the indices at which x is either 8 or 9. Then we can verify that at those indices, x is indeed 8 and 9.

```
> inds <- which(x %in% c(8,9))
> inds
[1] 1 3 4 12 15 19
> x[inds]
[1] 8 9 9 8 9 8
```

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