MATLAB Function Reference
union

Set union of two vectors

Syntax

• ```c = union(A,B)
c = union(A,B,'rows')
[c,ia,ib] = union(...)
```

Description

```c = union(A,B) ``` returns the combined values from `A` and B but with no repetitions. The resulting vector is sorted in ascending order. In set theoretic terms, `c = A ` B. A and B can be cell arrays of strings.

```c = union(A,B,'rows') ``` when `A `and `B `are matrices with the same number of columns returns the combined rows from `A` and `B `with no repetitions.

```[c,ia,ib] = union(...) ``` also returns index vectors `ia` and `ib` such that `c = a(ia)` `b(ib)`, or for row combinations, `c = a(ia,:)` `b(ib,:)`. If a value appears in both `a` and `b`, `union` indexes its occurrence in `b`. If a value appears more than once in `b` or in `a` (but not in `b`), `union` indexes the last occurrence of the value.

Examples

• ```a = [-1 0 2 4 6];
b = [-1 0 1 3];
[c,ia,ib] = union(a,b);
c =

-1     0     1     2     3     4     6

ia =

3     4     5

ib =

1     2     3     4
```

`intersect`, `setdiff`, `setxor`, `unique`, `ismember`, `issorted`