unique

Arguments

M

vector, matrix, or hypermatrix of numbers or strings.

orient

flag with possible values : 1 or "r", 2 or "c". It can't be used if M is an hypermatrix.

N

• If orient is not used: Vector of extracted M components sorted in ascending order.
• If orient is used: Matrix of extracted M rows or columns, sorted in lexicographic ascending order.

k

Vector of indices of first encountered occurences, such that N(i) = M(k(i)) or N(i,:) = M(k(i),:) or N(:,i) = M(:,k(i)).

Description

unique(M) returns a vector which retains the unique entries of M in ascending order.

unique(M,"r") or unique(M,1) removes all duplicates of M rows and returns unique rows in lexicographic ascending order.

unique(M,"c") or unique(M,2) removes all duplicates of M columns and returns unique columns in lexicographic ascending order.

Extracted components, rows or columns can be resorted in their initial order by sorting k. See the first example.

Examples

With some numbers:

M = int8([2  0  2  2  1  1  1  2  1  1  0  1  1  0  1  1
          0  1  2  0  1  2  2  0  1  1  2  0  1  0  0  0
          ])
[u, k] = unique(M)
[uc, kc] = unique(M, "c")

// Get unduplicated columns in initial order:
M(:, gsort(kc,"g","i"))

--> M 
 M = 
  2  0  2  2  1  1  1  2  1  1  0  1  1  0  1  1
  0  1  2  0  1  2  2  0  1  1  2  0  1  0  0  0

--> [u, k] = unique(M)
 u  =
  0
  1
  2

 k  =
   2.
   4.
   1.

--> [uc, kc] = unique(M, "c")
 uc  =
  0  0  0  1  1  1  2  2
  0  1  2  0  1  2  0  2

 kc  =
   14.   2.   11.   12.   5.   6.   1.   3.

--> // Get unduplicated columns in initial order:
--> M(:, gsort(kc,"g","i"))
 ans  =
  2  0  2  1  1  0  1  0
  0  1  2  1  2  2  0  0

With complex numbers:

i = %i;
c = [1+i, 1-i, -i, i, -i, 1+i]
[u, k] = unique(c)
[uc, kc] = unique(c, "c")

--> c = [1+i, 1-i, -i, i, -i, 1+i]
 c  =
   1. + i     1. - i  -i    i   -i    1. + i

--> [u, k] = unique(c)
 u  =
  -i    i    1. - i   1. + i

 k  =
   3.   4.   2.   1.

With some texts:

t = ["AB" "BA" "BA" "BA" "AB" "BA" "AB" "AB" "BB" "AA" "AB" "BA" "BA" "BA" "AA"
     "AA" "AA" "AB" "AA" "BB" "BB" "BB" "BA" "AB" "AB" "BB" "BB" "AB" "AB" "AA"
    ]
[u, k] = unique(t)
[uc, kc] = unique(t, "c")

 t  =
!AB  BA  BA  BA  AB  BA  AB  AB  BB  AA  AB  BA  BA  BA  AA  !
!AA  AA  AB  AA  BB  BB  BB  BA  AB  AB  BB  BB  AB  AB  AA  !

--> [u, k] = unique(t);
 u  =
!AA  !
!AB  !
!BA  !
!BB  !

 k  =
   2.
   1.
   3.
   10.

--> [uc, kc] = unique(t, "c")
 uc  =
!AA  AA  AB  AB  AB  BA  BA  BA  BB  !
!AA  AB  AA  BA  BB  AA  AB  BB  AB  !

 kc  =
   15.   10.   1.   8.   5.   2.   3.   6.   9.

See also

• members — count (and locate) in an array each element or row or column of another array
• gsort — sorting by quick sort algorithm
• vectorfind — finds in a matrix rows or columns matching a vector
• grep — find matches of a string in a vector of strings
• union — extract union components of a vector
• intersect — returns the unduplicated elements or rows or columns met in both input arrays

History