Question: I guess it is a very easy question.

```
v1 = 1:10
v2 = c(2,4,7)

```

(none of the numbers are repeated. No need to use `unique()`)

I want a vector containing all the values in v1 that are not in v2.

```
solution = c(1,3,5,6,8,9,10)

```

I can do this using a for loop but I'm sure there are easier solution.

Answer: 
```
setdiff(v1, v2)
# [1]  1  3  5  6  8  9 10

```
Use the `%in%` operator with logical NOT ( `!` ) to subset `v1` by values not in `v2`:

```
v1[ ! v1 %in% v2 ]
#[1]  1  3  5  6  8  9 10

```

Or you could look for non-matches of v1 in v2 (this is *almost* the same):

```
v1[ is.na( match( v1 , v2 ) ) ]
#[1]  1  3  5  6  8  9 10

```

Or using `which` to get the indices:

```
v1[  which( ! v1 %in% v2 ) ]
#[1]  1  3  5  6  8  9 10

```

All flavours of the same thing. And there are many more ways to do this. Definitely don't use a loop for this because this kind of operation is a perfect example of how you can take advatage of R's vectorisation. Loops are better to be called for their side-effects and/or when the processing to number of iterations ratio is large.