Determine if array is sorted
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Syntax
TF = issorted(A)
TF = issorted(A,dim)
TF = issorted(___,direction)
TF = issorted(___,Name,Value)
TF = issorted(A,'rows')
Description
TF = issorted(A) returns logical 1 (true) when the elements of A are in sorted order and logical 0 (false) otherwise.
If
Ais a vector, thenissortedreturns1 when the vector elements are in ascending order.If
Ais a matrix, thenissortedreturns1 when each column ofAis in ascending order.If
Ais a multidimensional array,thenissortedreturns 1 whenAisin ascending order along the first dimension whose size does not equal1.If
Ais a timetable, thenissortedreturns1 when its row time vector is in ascending order. To check the orderingof row times or variables of a timetable with additional options,use theissortedrowsfunction.
example
TF = issorted(A,dim) returns1 when A is sorted along dimension dim.For example, if A is a matrix, then issorted(A,2) returns1 when each row of A is in ascending order.
example
TF = issorted(___,direction) returns1 when A is sorted in the order specified by direction forany of the previous syntaxes. For example, issorted(A,'monotonic') returns1 if the elements of A are ascending or descending.
example
TF = issorted(___,Name,Value) specifiesadditional parameters for checking sort order. For example, issorted(A,'ComparisonMethod','abs') checksif A is sorted by magnitude.
example
TF = issorted(A,'rows') returns1 when the elements of the first column of a matrix are sorted. Ifthe first column contains repeated elements, then issorted looksat the ordering of the second column to determine TF.In general, issorted looks to the column immediatelyto the right to determine TF when the current andprevious columns have repeated elements.
If
Ais a timetable, thenissortedchecks if the row time vector is in ascending order.This syntax is not supported for a matrix of charactervectors.
Note
This syntax is not recommended. Use issortedrows instead.
Examples
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Sorted Vector
Open Live Script
Create a vector and check if it is sorted in ascending order.
A = [5 12 33 39 78 90 95 107];issorted(A)
ans = logical 1Sorted Matrix Rows
Open Live Script
Create a 5-by-5 matrix and check if each row is sorted in descending order.
A = magic(5)
A = 5×5 17 24 1 8 15 23 5 7 14 16 4 6 13 20 22 10 12 19 21 3 11 18 25 2 9issorted(A,2,'descend')ans = logical 0Sort each row of A in descending order using the sort function, and check that the result has descending rows.
B = sort(A,2,'descend')B = 5×5 24 17 15 8 1 23 16 14 7 5 22 20 13 6 4 21 19 12 10 3 25 18 11 9 2issorted(B,2,'descend')ans = logical 12-D Array of Strings
Open Live Script
Create a 2-D array of strings and determine if each column is sorted.
str = ["Horse","Chicken";"cow","Goat"]
str = 2x2 string "Horse" "Chicken" "cow" "Goat" issorted(str)
ans = logical 1Determine if the rows are sorted from left to right.
issorted(str,2)
ans = logical 0Determine if each row is sorted in descending order from left to right.
issorted(str,2,'descend')ans = logical 1Complex Vector with NaN
Open Live Script
Create a vector containing complex numbers and NaN values.
A = [NaN NaN 1+i 1+2i 2+2i 3+i];
Check that the NaN elements are placed first within the vector, and that the remaining elements are sorted by real part.
issorted(A,'MissingPlacement','first','ComparisonMethod','real')
ans = logical 1Since the third and fourth elements of A have equal real part, issorted checks if the imaginary part of these elements are also sorted.
imag(A(3))
ans = 1
imag(A(4))
ans = 2
Input Arguments
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A — Input array
vector | matrix | multidimensional array | cell array of character vectors | timetable
Input array, specified as a vector, matrix, multidimensionalarray, cell array of character vectors, or timetable.
If
Acontains missing values, suchasNaN,NaT,<undefined>,andmissing, then by default,issortedrequiresthat they are placed at the end to return 1.If
Ais complex, then by default,issorteddeterminessort order by the magnitude of the elements. If there are consecutiveelements with equal magnitude, thenissortedalsochecks the phase angle in the interval (-π, π] to breakties.If
Ais a cell array of charactervectors or a string array, thenissorteddeterminessort order using the code order for the UTF-16 character encodingscheme. The sort is case-sensitive. For more information on sortedcharacter and string arrays, see Sort Order for Character and String Arrays.
Data Types: double | single | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical | char | string | cell | categorical | datetime | duration | timetable
Complex Number Support: Yes
dim — Dimension to operate along
positive integer scalar
Dimension to operate along, specified as a positive integerscalar. If no value is specified, then the default is the first arraydimension whose size does not equal 1.
Consider a matrix A. issorted(A,1) checksif the data in each column of A is sorted.
issorted(A,2) checks if the data in eachrow of A is sorted.
dim is not supported for timetable input.
Data Types: double | single | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64
direction — Sorting direction
'ascend' (default) | 'descend' | 'monotonic' | 'strictascend' | 'strictdescend' | 'strictmonotonic'
Sorting direction, specified as one of the following:
'ascend'— Checks if datais in ascending order. Data can contain consecutive repeated elements.'descend'— Checks if datais in descending order. Data can contain consecutive repeated elements.'monotonic'— Checks ifdata is in descending or ascending order. Data can contain consecutiverepeated elements.'strictascend'— Checks if data is in strictly ascending order. Data cannot contain duplicate or missing elements.'strictdescend'— Checks if data is in strictly descending order. Data cannot contain duplicate or missing elements.'strictmonotonic'— Checks if data is in strictly descending or strictly ascending order. Data cannot contain duplicate or missing elements.
direction is not supported for timetableinput. Use issortedrows instead.
Name-Value Arguments
Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.
Before R2021a, use commas to separate each name and value, and enclose Name in quotes.
Example: issorted(A,'MissingPlacement','last')
MissingPlacement — Placement of missing values
'auto' (default) | 'first' | 'last'
Placement of missing values (NaN, NaT, <undefined>,and missing) specified as the comma-separated pairconsisting of 'MissingPlacement' and one of thefollowing:
'auto'— Missing elementsare required to be placed last for ascending order and first for descendingorder to return 1.'first'— Missing elementsare required to be placed first to return 1.'last'— Missing elementsare required to be placed last to return 1.
This name-value pair is not supported for timetable input. Use issortedrows instead.
ComparisonMethod — Element comparison method
'auto' (default) | 'real' | 'abs'
Element comparison method for numeric input, specified as the comma-separated pair consisting of 'ComparisonMethod' and one of the following:
'auto'— Check ifAis sorted byreal(A)whenAis real, and check ifAis sorted byabs(A)whenAis complex.'real'— Check ifAis sorted byreal(A)whenAis real or complex. IfAhas elements with consecutive equal real parts, then checkimag(A)to break ties.'abs'— Check ifAis sorted byabs(A)whenAis real or complex. IfAhas elements with consecutive equal magnitude, then checkangle(A)in the interval (-π,π] to break ties.
More About
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Sort Order for Character and String Arrays
MATLAB® stores characters as Unicode® usingthe UTF-16 character encoding scheme. Character and string arraysare sorted according to the UTF-16 code point order. For the charactersthat are also the ASCII characters, this order means that uppercaseletters come before lowercase letters. Digits and some punctuationalso come before letters.
Extended Capabilities
Tall Arrays
Calculate with arrays that have more rows than fit in memory.
The issorted function fully supports tall arrays. For more information, see Tall Arrays.
C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.
Usage notes and limitations:
The first input argument must not be a cell array.
If
Ais complex with all zero imaginary parts, then MATLAB might convertAtoreal(A)before callingissorted(A). In this case, MATLAB checks thatAis sorted byreal(A), but the generated code checks thatAis sorted byabs(A). To make the generated code match MATLAB, useissorted(real(A))orissorted(A,'ComparisonMethod','real'). See Code Generation for Complex Data with Zero-Valued Imaginary Parts (MATLAB Coder).If you supply
dim, then it must be constant.For limitations related to variable-size inputs, see Variable-Sizing Restrictions for Code Generation of Toolbox Functions (MATLAB Coder).
Thread-Based Environment
Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool.
This function fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.
GPU Arrays
Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.
The issorted function supports GPU array input with these usage notes and limitations:
The input array
Amust be a vector.The
MissingPlacementname-value option supports only the value'auto'.
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™.
This function fully supports distributed arrays. For more information, see Run MATLAB Functions with Distributed Arrays (Parallel Computing Toolbox).
Version History
Introduced before R2006a
See Also
sort | sortrows | issortedrows
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