union (MATLAB Function Reference)

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 occurence in b. If a value appears more than once in b or in a (but not in b), union indexes the last occurence 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

See Also

intersect, setdiff, setxor, unique

undocheckout unique