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See the recommended documentation of this function
unique
extracts (and sorts) distinct elements, rows or columns of a matrix
Syntax
[N, km, kn, nb] = unique(M) [N, km, kn, nb] = unique(M, orient) [N, km, kn, nb] = unique(.., "keepOrder") [N, km, kn, nb] = unique(.., "uniqueNan")
Arguments
 M
 vector, matrix, or hypermatrix of numbers or of 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 extractedM
components sorted in ascending order. IfM
is a row vector,N
is also a row vector. In all otherM
cases,N
is a matrix or a column vector.  If
orient
is used: Matrix of extractedM
rows or columns, sorted in lexicographic ascending order.
 If
 km
 Vector of indices of first encountered occurrences, such that
N(i) = M(km(i))
orN(i,:) = M(km(i),:)
orN(:,i) = M(:,km(i))
.km
is a row ifM
is a row or iforient="c"
is used. Otherwise it's a column.  kn
 Not yet implemented.
Vector of indices of first encountered occurrences, such that
M(i) = N(kn(i))
orM(i,:) = N(kn(i),:)
orM(:,i) = N(:,kn(i))
.  nb
 Vector of integers > 0, with the same
km
shape: Numbers of occurrences inM
of respective unduplicated entities (components, rows, columns) returned inN
.
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.
unique(M,.. "keepOrder")
returns M
unduplicated
entries in their original order in M
.
"keepOrder"
is caseinsensitive.
unique(M,.. "uniqueNan")
considers all Nan values as the same one,
and unduplicates them. By default, any Nan is different
from any other Nan, including itself: %nan<>%nan
is true, unless
"uniqueNan"
is used. Specifying
"uniqueNan"
is caseinsensitive.
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, km] = unique(M) [uc, kmc] = unique(M, "c")
> 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, km] = unique(M) u = 0 1 2 km = 2. 4. 1. > [uc, kmc] = unique(M, "c") uc = 0 0 0 1 1 1 2 2 0 1 2 0 1 2 0 2 kmc = 14. 2. 11. 12. 5. 6. 1. 3.
With complex numbers:
i = %i; c = [1+i, 1i, i, i, i, 1+i] [u, k] = unique(c) [uc, kc] = unique(c, "c")
> c = [1+i, 1i, 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 = ["BA" "BB" "AB" "BA" "AB" "BA" "AB" "AB" "BA" "AA" "AB" "BA" "BA" "BA" "AA" "AA" "AB" "AA" "AA" "BB" "BB" "BB" "BA" "AB" "AB" "BB" "BB" "AB" "AB" "AA" ] u = unique(t)' [u, kt, ku, nb] = unique(t(1,:)) [u, kt] = unique(t(1,:), "keepOrder") // Keeping the original order of row#1 elements [uc, ktc, kuc, nb] = unique(t, "c") [uc, ktc, kuc, nb] = unique(t, "c", "keepOrder") // Keeping the original order of columns
> t = ["BA" "BB" "AB" "BA" "AB" "BA" "AB" "AB" "BA" "AA" "AB" "BA" "BA" "BA" "AA" > "AA" "AB" "AA" "AA" "BB" "BB" "BB" "BA" "AB" "AB" "BB" "BB" "AB" "AB" "AA" > ] t = !BA BB AB BA AB BA AB AB BA AA AB BA BA BA AA ! !AA AB AA AA BB BB BB BA AB AB BB BB AB AB AA ! > u = unique(t)' u = !AA AB BA BB ! > [u, kt, ku, nb] = unique(t(1,:)); u, kt, nb u = !AA AB BA BB ! kt = 10. 3. 1. 2. nb = 2. 5. 7. 1. > [u, kt] = unique(t(1,:), "keepOrder") // Keeping the original order u = !BA BB AB AA ! kt = 1. 2. 3. 10. > [uc, ktc, kuc, nb] = unique(t, "c") uc = !AA AA AB AB AB BA BA BA BB ! Sorted columns !AA AB AA BA BB AA AB BB AB ! ktc = 15. 10. 3. 8. 5. 1. 9. 6. 2. nb = 1. 1. 1. 1. 3. 2. 3. 2. 1. > [uc, ktc, kuc, nb] = unique(t, "c", "keepOrder") // Keeping the original order uc = !BA BB AB AB BA AB BA AA AA ! !AA AB AA BB BB BA AB AB AA ! ktc = 1. 2. 3. 5. 6. 8. 9. 10. 15. nb = 2. 1. 1. 3. 2. 1. 3. 1. 1.
With Nan (and Inf) values. "uniqueNan" option:
M = [2 2 %nan 1 2 0 1 %nan 0 %nan 1 0 1 %nan 0 %inf 0 1 %inf 1 ]; [v, km, kv, n] = unique(M); v',n' [v, km, kv, n] = unique(M, "uniqueNan"); v',n' unique(M, "c") [v, kmc, kvc, n] = unique(M, "c", "uniqueNan")
> M M = 2. 2. Nan 1. 2. 0. 1. Nan 0. Nan 1. 0. 1. Nan 0. Inf 0. 1. Inf 1. > [v, km, kv, n] = unique(M); v',n' ans = 0. 1. 2. Inf Nan Nan Nan Nan ans = 5. 6. 3. 2. 1. 1. 1. 1. > [v, km, kv, n] = unique(M, "uniqueNan"); v',n' ans = 0. 1. 2. Inf Nan ans = 5. 6. 3. 2. 4. > unique(M, "c") ans = 0. 1. 1. 2. 2. Nan Nan Nan Inf 0. Nan 0. 1. 1. 1. 1. > [v, kmc, kvc, n] = unique(M, "c", "uniqueNan") v = 0. 1. 1. 2. 2. Nan Inf 0. Nan 0. 1. 1. kmc = 6. 7. 4. 2. 1. 3. n = 2. 1. 1. 2. 1. 3.
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 — locates occurences of a (wildcarded) vector in a matrix or hypermatrix
 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
Version  Description 
6.0.2  unique() can now be used to unduplicate complex numbers. 
6.1.0 

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