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maxk

Find k largest elements of array

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Syntax

B = maxk(A,k)
B = maxk(A,k,dim)
B = maxk(___,'ComparisonMethod',c)
[B,I] = maxk(___)

Description

B = maxk(A,k) returns the k largest elements of A.

  • If A is a vector, then maxk returns a vector containing the k largest elements of A.

  • If A is a matrix, then maxk returns a matrix whose columns contain the k largest elements of each column of A.

  • If A is a multidimensional array, then maxk returns the k largest elements along the first dimension whose size does not equal 1.

example

B = maxk(A,k,dim) determines the k largest elements of A along dimension dim.

example

B = maxk(___,'ComparisonMethod',c) optionally specifies how to compare elements of A for any of the previous syntaxes. For example, maxk(A,k,'ComparisonMethod','abs') returns the k largest elements of A according to their absolute values.

example

[B,I] = maxk(___) finds the indices of the largest k values of A and returns them in I.

example

Examples

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Open Live Script

Compute the largest 3 elements of a vector.

A = 1:10;
B = maxk(A,3)
B = 1×3

    10     9     8
Open Live Script

Compute the largest 3 elements of each row of a matrix. 

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


B = maxk(A,3,2)
B = 5×3

    24    17    15
    23    16    14
    22    20    13
    21    19    12
    25    18    11
Open Live Script

Compute the 2 largest elements of a complex vector according to their magnitude, and return the indices where they are located in the input vector. 

A = [2-2i 5+i -7-3i -1+i]
A = 1×4 complex

   2.0000 - 2.0000i   5.0000 + 1.0000i  -7.0000 - 3.0000i  -1.0000 + 1.0000i


[B,I] = maxk(A,2,'ComparisonMethod','abs')
B = 1×2 complex

  -7.0000 - 3.0000i   5.0000 + 1.0000i


I = 1×2

     3     2

Input Arguments

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Input array, specified as a vector, matrix, or multidimensional array.

  • If A is a vector, then maxk returns a vector containing the k largest elements of A.

  • If A is a matrix, then maxk returns a matrix whose columns contain the k largest elements of each column of A.

  • If A is a multidimensional array, then maxk returns the k largest elements along the first dimension whose size does not equal 1.

If A has type categorical, then it must be ordinal.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical | char | categorical | datetime | duration
Complex Number Support: Yes

Number of maxima to return, specified as a positive integer scalar. If k is greater than or equal to the number of elements in the operating dimension, then maxk sorts the input array along that dimension.

Operating dimension, 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 an m-by-n input matrix, A:

  • maxk(A,k,1) computes the k largest values in each column of A and returns a k-by-n matrix.

    maxk(A,k,1) column-wise operation

  • maxk(A,k,2) computes the k largest values in each row of A and returns an m-by-k matrix.

    maxk(A,k,2) row-wise operation

Comparison method, specified as one of the following:

  • 'auto' — Compare elements of input A by real(A) when A is real, and by abs(A) when A is complex.

  • 'real' — Compare elements of input A by real(A) when A is real or complex. If A has elements with equal real parts, then use imag(A) to break ties.

  • 'abs' — Compare elements of input A by abs(A) when A is real or complex. If A has elements with equal magnitude, then use angle(A) in the interval (-π,π] to break ties.

Output Arguments

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Output array, returned as a scalar, vector, matrix, or multidimensional array. maxk returns the k elements in order from largest to smallest. The order of the elements in B preserves the order of any equal elements in A.

Index array, returned as a vector, matrix, or multidimensional array. I is the same size as B. If the output array B contains repeated elements, then the order of their indices in I matches the order in which they appear in the input array.

Extended Capabilities

Version History

Introduced in R2017b

See Also

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