union extract union components of a vector

## Syntax

                [v [,ka, kb] ] = union(a,b)
                [v [,ka, kb] ] = union(a,b,orient)

## Arguments

a

  vector or matrix of numbers or strings

b

  vector of real numbers or strings

orient

  flag with possible values : 1 or "r", 2 or "c".

v

  row vector or matrix of numbers or strings

ka

  row vector of integers

kb

  row vector of integers

## Description

`union(a,b)` returns a sorted row vector which retains the unique entries of `[a(:);b(:)]`.

`union(a,b,"r")` or `union(a,b,1)`returns the matrix formed by the union of the unique rows of `a` and `b` sorted in lexicographic ascending order. In this case matrices `a` and `b` must have the same number of columns.

`union(a,b,"c")` or `union(a,b,2)`returns the matrix formed by the union of the unique columns of `a` and `b` sorted in lexicographic ascending order. In this case matrices `a` and `b` must have the same number of rows.

`[v,ka,kb]=union(a,b)` also returns index vectors `ka` and `kb` such that `v` is a sorted combination of the entries `a(ka)` and `b(kb)`.

## Examples

    A=round(5*rand(10,1));
    B=round(5*rand(7,1));

    union(A,B)
    [N,ka,kb]=union(A,B)

    union('a'+string(A),'b'+string(B))

## See also

- unique
- gsort