allunique

R2026b

Determine if all values are unique

Since R2025a

Syntax

tf = allunique(A)

tf = allunique(A,"rows")

Description

tf = allunique(A) returns logical 1 (true) if all values in A are unique. Otherwise, allunique returns logical 0 (false). If A is a table, allunique behaves as if you called allunique(A,"rows").

tf = allunique(A,"rows") treats each row of A as a single entity and returns logical 1 (true) if every row is unique.

The "rows" option does not support cell arrays.

Examples

Unique Values in Vector

Create a vector with repeated values. Then, determine if all elements in the vector have a unique value.

A = [9; 2; 9; 9; 5; 2];
tf = allunique(A)

tf = logical
   0

Vector Containing Missing Values

Create a vector containing missing values. Then, determine if all elements in the vector have a unique value. allunique treats each instance of a missing value as a distinct value.

A = [5; 8; NaN; NaN];
tf = allunique(A)

tf = logical
   1

String with Trailing White Space

Create a string array, where one of the strings has trailing white space. Then, determine if all elements in the array have a unique value. allunique treats the string with trailing white space as a distinct string.

A = ["dog" "cat" "horse" "dog "];
tf = allunique(A)

tf = logical
   1

Repeated Rows in Matrix

Create a matrix with some repeated values. Then, determine if all values in the matrix are unique.

A = [1 2; 2 1; 3 4; 4 3]

A = 4×2

     1     2
     2     1
     3     4
     4     3

tfVal = allunique(A)

tfVal = logical
   0

Determine if all rows in the matrix are unique.

tfRow = allunique(A,"rows")

tfRow = logical
   1

Repeated Rows in Table

Create a table with some repeated rows.

A = [38; 43; 38; 40];
B = logical([1; 0; 1; 1]);
T = table(A,B,RowNames=["Smith" "Johnson" "Williams" "Jones"])

T = 4×2 table
                A       B  
                __    _____

    Smith       38    true 
    Johnson     43    false
    Williams    38    true 
    Jones       40    true 

Determine if all rows in the table are unique. For tabular data, allunique always behaves as if you specified the "rows" option, and it ignores row names. So, the first and third rows are considered repeated rows.

tf = allunique(T)

tf = logical
   0

Input Arguments

A — Input data

array | table | timetable

Input data, specified as an array, table, or timetable.

• If A is a table, then allunique does not take row names into account. Two rows that have the same values but different names are considered equal.

• If A is a timetable, then allunique takes row times into account. Two rows that have the same values but different times are not considered equal.

• If A is a categorical array, then the sort order is determined by the order of the categories. To see the sort order of a categorical array, use the categories function.

A can also be an object with the class method unique or these class methods:

• sort (or sortrows, if you specify the "rows" option)

• ne (not equal)

The methods must not have conflicting behaviors or outcomes. sort or sortrows must use a stable sorting algorithm. For example, you can specify A as a heterogeneous array derived from a common root class, such as an array of graphics objects.

allunique treats missing values and strings with trailing white space as unique values.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™. (since R2026b)

GPU Code Generation
Generate CUDA® code for NVIDIA® GPUs using GPU Coder™. (since R2026b)

GPU Arrays

Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™. (since R2026a)

The allunique function supports GPU array input with these usage notes and limitations:

• Sparse array inputs are not supported.

For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).

Distributed Arrays

Partition large arrays across the combined memory of your cluster using Parallel Computing Toolbox™. (since R2026a)

The allunique function supports distributed arrays with these usage notes and limitations:

• Table, timetable, datetime, and calendar duration inputs are not supported.

For more information, see Run MATLAB Functions with Distributed Arrays (Parallel Computing Toolbox).

Version History

Introduced in R2025a

R2026b: Code generation support

Generate C or C++ code for the allunique function.