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# issorted

Determine if array is sorted

## Syntax

TF = issorted(A)
TF = issorted(A,dim)
TF = issorted(___,direction)
TF = issorted(___,Name,Value)
TF = issorted(A,'rows')

## Description

example

TF = issorted(A) returns the logical scalar 1 (true) when the elements of A are listed in ascending order and 0 (false) otherwise.

• If A is a vector, then issorted returns 1 when the vector elements are in ascending order.

• If A is a matrix, then issorted returns 1 when each column of A is in ascending order.

• If A is a multidimensional array, then issorted returns 1 when A is in ascending order along the first dimension whose size does not equal 1.

• If A is a timetable, then issorted returns 1 when its row time vector is in ascending order. To check the ordering of row times or variables of a timetable with additional options, use the issortedrows function.

example

TF = issorted(A,dim) returns 1 when A is sorted along dimension dim. For example, if A is a matrix, then issorted(A,2) returns 1 when each row of A is in ascending order.

example

TF = issorted(___,direction) returns 1 when A is sorted in the order specified by direction for any of the previous syntaxes. For example, issorted(A,'monotonic') returns 1 if the elements of A are ascending or descending.

example

TF = issorted(___,Name,Value) specifies additional parameters for checking sort order. For example, issorted(A,'ComparisonMethod','abs') checks if A is sorted by magnitude.

TF = issorted(A,'rows') returns 1 when the elements of the first column of a matrix are sorted. If the first column contains repeated elements, then issorted looks at the ordering of the second column to determine TF. In general, issorted looks to the column immediately to the right to determine TF when the current and previous columns have repeated elements.

• If A is a timetable, then issortedrows checks if the row time vector is in ascending order.

• This syntax is not supported for a matrix of character vectors.

### Note

This syntax is not recommended. Use issortedrows instead.

## Examples

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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
1

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     9

issorted(A,2,'descend')
ans = logical
0

Sort 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     2

issorted(B,2,'descend')
ans = logical
1

Create a 2-D array of strings and determine if each column is sorted.

str = string({'Horse','Chicken';'cow','Goat'})
str = 2x2 string array
"Horse"    "Chicken"
"cow"      "Goat"

issorted(str)
ans = logical
1

Determine if the rows are sorted from left to right.

issorted(str,2)
ans = logical
0

Determine if each row is sorted in descending order from left to right.

issorted(str,2,'descend')
ans = logical
1

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
1

Since 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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Input array, specified as a vector, matrix, multidimensional array, cell array of character vectors, or timetable.

• If A contains missing values, such as NaN, NaT, <undefined>, and missing, then by default, issorted requires that they are placed at the end to return 1.

• If A is complex, then by default, issorted determines sort order by the magnitude of the elements. If there are consecutive elements with equal magnitude, then issorted also checks the phase angle in the interval (-π, π] to break ties.

• If A is a cell array of character vectors or a string array, then issorted determines sort order using the code order for the UTF-16 character encoding scheme. The sort is case-sensitive. For more information on sorted character 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

Dimension to operate along, specified as a positive integer scalar. If no value is specified, then the default is the first array dimension whose size does not equal 1.

Consider a matrix A. issorted(A,1) checks if the data in each column of A is sorted.

issorted(A,2) checks if the data in each row of A is sorted.

dim is not supported for timetable input.

Data Types: double | single | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Sorting direction, specified as one of the following:

• 'ascend' — Checks if data is in ascending order. Data can contain consecutive repeated elements.

• 'descend' — Checks if data is in descending order. Data can contain consecutive repeated elements.

• 'monotonic' — Checks if data is in descending or ascending order. Data can contain consecutive repeated 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 timetable input. Use issortedrows instead.

### Name-Value Pair Arguments

Specify optional comma-separated pairs of Name,Value arguments. Name is the argument name and Value is the corresponding value. Name must appear inside quotes. You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

Example: issorted(A,'MissingPlacement','last')

Placement of missing values (NaN, NaT, <undefined>, and missing) specified as the comma-separated pair consisting of 'MissingPlacement' and one of the following:

• 'auto' — Missing elements are required to be placed last for ascending order and first for descending order to return 1.

• 'first' — Missing elements are required to be placed first to return 1.

• 'last' — Missing elements are required to be placed last to return 1.

This name-value pair is not supported for timetable input. Use issortedrows instead.

Element comparison method, specified as the comma-separated pair consisting of 'ComparisonMethod' and one of the following:

• 'auto' — Check if A is sorted by real(A) when A is real, and check if A is sorted by abs(A) when A is complex.

• 'real' — Check if A is sorted by real(A) when A is real or complex. If A has elements with consecutive equal real parts, then check imag(A) to break ties.

• 'abs' — Check if A is sorted by abs(A) when A is real or complex. If A has elements with consecutive equal magnitude, then check angle(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® using the UTF-16 character encoding scheme. Character and string arrays are sorted according to the UTF-16 code point order. For the characters that are also the ASCII characters, this order means that uppercase letters come before lowercase letters. Digits and some punctuation also come before letters.

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