# issubset

```
.. issubset(A, S) -> Bool
âŠ†(A,S) -> Bool
Return ``true`` if ``A`` is a subset of or equal to ``S``.
```

## Examples

**Check if every element of a is in b:**

```
julia> issubset([1, 2, 3], [1, 2, 3, 4, 5])
true
```

This example checks if every element in `[1, 2, 3]`

is present in `[1, 2, 3, 4, 5]`

. Since all elements are present, it returns `true`

.

```
julia> issubset([4, 5, 6], [1, 2, 3])
false
```

In this case, not all elements in `[4, 5, 6]`

are present in `[1, 2, 3]`

, so it returns `false`

.

**Check if a is a proper subset of b:**

```
julia> issubset([1, 2], [1, 2, 3])
true
```

Here, `[1, 2]`

is a proper subset of `[1, 2, 3]`

, so it returns `true`

.

```
julia> issubset([1, 2, 3], [1, 2, 3])
false
```

Since `[1, 2, 3]`

is not a proper subset of itself, it returns `false`

.

**Check if a is not a subset of b:**

```
julia> issubset([4, 5, 6], [1, 2, 3])
true
```

In this example, `[4, 5, 6]`

is not a subset of `[1, 2, 3]`

, so it returns `true`

.

```
julia> issubset([1, 2, 3], [1, 2, 3])
false
```

Since `[1, 2, 3]`

is a subset of itself, it returns `false`

.

Common mistake example:

```
julia> issubset([1, 2, 3], 4)
ERROR: MethodError: no method matching issubset(::Array{Int64,1}, ::Int64)
```

In this example, the second argument provided is not an iterable collection. The `issubset`

function expects both arguments to be collections that can be iterated over. Make sure to provide valid collections as arguments to `issubset`

.

## See Also

complement, complement!, intersect, intersect!, issubset, selectperm, selectperm!, Set, setdiff, setdiff!, symdiff, union, union!,## User Contributed Notes

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