median

Median value of array

Syntax

Description

example

M = median(A) returns the median value of A.

  • If A is a vector, then median(A) returns the median value of A.

  • If A is a nonempty matrix, then median(A) treats the columns of A as vectors and returns a row vector of median values.

  • If A is an empty 0-by-0 matrix, median(A) returns NaN.

  • If A is a multidimensional array, then median(A) treats the values along the first array dimension whose size does not equal 1 as vectors and returns an array of median values. The size of this dimension becomes 1 while the sizes of all other dimensions remain the same.

median computes natively in the numeric class of A, such that class(M) = class(A).

example

M = median(A,dim) returns the median of elements along dimension dim. For example, if A is a matrix, then median(A,2) is a column vector containing the median value of each row.

Examples

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Median of Matrix Columns

Define a 4-by-3 matrix.

A = [0 1 1; 2 3 2; 1 3 2; 4 2 2]
A =

     0     1     1
     2     3     2
     1     3     2
     4     2     2

Find the median value of each column.

M = median(A)
M =

    1.5000    2.5000    2.0000

For each column, the median value is the mean of the middle two numbers in sorted order.

Median of Matrix Rows

Define a 2-by-3 matrix.

A = [0 1 1; 2 3 2]
A =

     0     1     1
     2     3     2

Find the median value of each row.

M = median(A,2)
M =

     1
     2

For each row, the median value is the middle number in sorted order.

Median of 3-D Array

Create a 1-by-3-by-4 array of integers between 1 and 10.

A = gallery('integerdata',10,[1,3,4],1)
A(:,:,1) =

    10     8    10


A(:,:,2) =

     6     9     5


A(:,:,3) =

     9     6     1


A(:,:,4) =

     4     9     5

Find the median values of this 3-D array along the second dimension.

M = median(A)
M(:,:,1) =

    10


M(:,:,2) =

     6


M(:,:,3) =

     6


M(:,:,4) =

     5

This operation produces a 1-by-1-by-4 array by computing the median of the three values along the second dimension. The size of the second dimension is reduced to 1.

Compute the median along the first dimension of A.

M = median(A,1);
isequal(A,M)
ans =

     1

This returns the same array as A because the size of the first dimension is 1.

Median of 8-bit Integer Array

Define a 1-by-4 vector of 8-bit integers.

A = int8(1:4)
A =

    1    2    3    4

Compute the median value.

M = median(A),
class(M)
M =

    3


ans =

int8

M is the mean of the middle two numbers in sorted order returned as an 8-bit integer.

Input Arguments

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A — Input arrayvector | matrix | multidimensional array

Input array, specified as a vector, matrix, or multidimensional array. A can be a numeric array, ordinal categorical array, datetime array, or duration array.

If A contains NaN or NaT (Not a Time), then median returns NaN or NaT. Undefined values in categorical arrays are similar to NaNs in numeric arrays.

dim — Dimension to operate alongpositive integer scalar

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

Dimension dim indicates the dimension whose length reduces to 1. The size(M,dim) is 1, while the sizes of all other dimensions remain the same.

Consider a two-dimensional input array, A.

  • If dim = 1, then median(A,1) returns a row vector containing the median of the elements in each column.

  • If dim = 2, then median(A,2) returns a column vector containing the median of the elements in each row.

median returns A if dim is greater than ndims(A).

More About

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Algorithms

For ordinal categorical arrays, MATLAB® interprets the median of an even number of elements as follows:

If the number of categories between the middle two values is ...Then the median is ...
zero (values are from consecutive categories)larger of the two middle values
an odd numbervalue from category occurring midway between the two middle values
an even numbervalue from larger of the two categories occurring midway between the two middle values

See Also

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