mean

Average or mean value of array

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Syntax

M = mean(A)

M = mean(A,'all')

M = mean(A,dim)

M = mean(A,vecdim)

M = mean(___,outtype)

M = mean(___,nanflag)

Description

example

M = mean(A)returns themeanof the elements ofAalong the first array dimension whose size does not equal 1.

IfAis a vector, thenmean(A)returns the mean of the elements.
IfAis a matrix, thenmean(A)returns a row vector containing the mean of each column.
IfAis a multidimensional array, thenmean(A)operates along the first array dimension whose size does not equal 1, treating the elements as vectors. This size of this dimension becomes1while the sizes of all other dimensions remain the same asA.

example

M = mean(A,'all')computes the mean over all elements ofA. This syntax is valid for MATLAB^®versions R2018b and later.

example

M = mean(A,dim)returns the mean along dimensiondim. For example, ifAis a matrix, thenmean(A,2)is a column vector containing the mean of each row.

example

M = mean(A,vecdim)computes the mean based on the dimensions specified in the vectorvecdim. For example, ifAis a matrix, thenmean(A,[1 2])is the mean of all elements inA, since every element of a matrix is contained in the array slice defined by dimensions 1 and 2.

example

M = mean(___,outtype)returns the mean with a specified data type, using any of the input arguments in the previous syntaxes.outtypecan be'default','double', or'native'.

example

M = mean(___,nanflag)specifies whether to include or omitNaNvalues from the calculation for any of the previous syntaxes.mean(A,'includenan')includes allNaNvalues in the calculation whilemean(A,'omitnan')ignores them.

Examples

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Mean of Matrix Columns

Open Live Script

Create a matrix and compute the mean of each column.

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

A =4×30 1 1 2 3 2 1 3 2 4 2 2

M = mean(A)

M =1×31.7500 2.2500 1.7500

Mean of Matrix Rows

Open Live Script

Create a matrix and compute the mean of each row.

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

A =4×30 1 1 2 3 2 3 0 1 1 2 3

M = mean(A,2)

M =4×10.6667 2.3333 1.3333 2.0000

Mean of 3-D Array

Open Live Script

Create a 4-by-2-by-3 array of integers between 1 and 10 and compute the mean values along the second dimension.

rng('default') A = randi(10,[4,2,3]); M = mean(A,2)

M = M(:,:,1) = 8.0000 5.5000 2.5000 8.0000 M(:,:,2) = 10.0000 7.5000 5.5000 6.0000 M(:,:,3) = 6.0000 5.5000 8.5000 10.0000

Mean of Array Page

Open Live Script

Create a 3-D array and compute the mean over each page of data (rows and columns).

A(:,:,1) = [2 4; -2 1]; A(:,:,2) = [9 13; -5 7]; A(:,:,3) = [4 4; 8 -3]; M1 = mean(A,[1 2])

M1 = M1(:,:,1) = 1.2500 M1(:,:,2) = 6 M1(:,:,3) = 3.2500

Starting in R2018b, to compute the mean over all dimensions of an array, you can either specify each dimension in the vector dimension argument, or use the'all'option.

M2 = mean(A,[1 2 3])

M2 = 3.5000

Mall = mean(A,'all')

Mall = 3.5000

Mean of Single-Precision Array

Open Live Script

Create a single-precision vector of ones and compute its single-precision mean.

A = single(ones(10,1)); M = mean(A,'native')

M =single1

The result is also in single precision.

class(M)

ans = 'single'

Mean Excluding`NaN`

Open Live Script

Create a vector and compute its mean, excludingNaNvalues.

A = [1 0 0 1 NaN 1 NaN 0]; M = mean(A,'omitnan')

M = 0.5000

If you do not specify'omitnan', thenmean(A)returnsNaN.

Input Arguments

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`A`—Input array
vector|matrix|multidimensional array

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

IfAis a scalar, thenmean(A)returnsA.
IfAis an empty 0-by-0 matrix, thenmean(A)returnsNaN.

`dim`—Dimension to operate along
positive integer scalar

Dimension to operate along, specified as a positive integer scalar. If you do not specify the dimension, then the default is the first array dimension of size greater than 1.

Dimensiondimindicates the dimension whose length reduces to1. Thesize(M,dim)is1, while the sizes of all other dimensions remain the same.

Consider anm-by-ninput matrix,A:

mean(A,1)computes the mean of the elements in each column ofAand returns a1-by-nrow vector.
mean(A,2)computes the mean of the elements in each row ofAand returns anm-by-1column vector.

meanreturnsAwhendimis greater thanndims(A)or whensize(A,dim)is1.

`vecdim`—Vector of dimensions
vector of positive integers

Vector of dimensions, specified as a vector of positive integers. Each element represents a dimension of the input array. The lengths of the output in the specified operating dimensions are 1, while the others remain the same.

Consider a 2-by-3-by-3 input array,A. Thenmean(A,[1 2])returns a 1-by-1-by-3 array whose elements are the means over each page ofA.

Mapping of a 2-by-3-by-3 input array to a 1-by-1-by-3 output array

`outtype`—Output data type
`'default'`(default) |`'double'`|`'native'`

Output data type, specified as'default','double', or'native'. These options also specify the data type in which the operation is performed.

`outtype`	Output data type
`'default'`	`double`, unless the input data type is`single`,`duration`, or`datetime`, in which case, the output is`'native'`
`'double'`	`double`, unless the data type is`duration`or`datetime`, in which case,`'double'`is not supported
`'native'`	Same data type as the input, unless Input data type is`logical`, in which case, the output is`double` Input data type is`char`, in which case,`'native'`is not supported

Data Types:char

`nanflag`—`NaN`condition
`“includenan”`(default) |`'omitnan'`

NaNcondition, specified as one of these values:

“includenan”— IncludeNaNvalues when computing the mean, resulting inNaN.
'omitnan'— Ignore allNaNvalues in the input.

Fordatetimearrays, you can also use'omitnat'or'includenat'to omit and includeNaTvalues, respectively.

Data Types:char

More About

collapse all

Mean

For a random variable vectorAmade up ofNscalar observations, the mean is defined as

$μ = \frac{1}{N} \sum_{i = 1}^{N} A_{i} .$

Extended Capabilities

Tall Arrays
Calculate with arrays that have more rows than fit in memory.

This function fully supports tall arrays. For more information, seeTall Arrays.

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

If you specifydim, then it must be a constant.
Theouttypeandnanflagoptions must be constant character vectors.
Integer types do not support the'native'output data type option.
SeeVariable-Sizing Restrictions for Code Generation of Toolbox Functions(MATLAB Coder).

GPU Code Generation
Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

Usage notes and limitations:

If you specifydim, then it must be a constant.
Theouttypeandnanflagoptions must be constant character vectors.
Integer types do not support the'native'output data type option.

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, seeRun MATLAB Functions in Thread-Based Environment.

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

Usage notes and limitations:

The'native'option is not supported.

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

Distributed Arrays
Partition large arrays across the combined memory of your cluster using Parallel Computing Toolbox™.

Usage notes and limitations:

The'native'option is not supported.

For more information, see运行MATLAB函数与分布式阵列(Parallel Computing Toolbox).

版本历史

Introduced before R2006a

mean

Syntax

Description

Examples

Mean of Matrix Columns

Mean of Matrix Rows

Mean of 3-D Array

Mean of Array Page

Mean of Single-Precision Array

Mean ExcludingNaN

Input Arguments

A—Input arrayvector|matrix|multidimensional array

dim—Dimension to operate alongpositive integer scalar

vecdim—Vector of dimensionsvector of positive integers

outtype—Output data type'default'(default) |'double'|'native'

nanflag—NaNcondition“includenan”(default) |'omitnan'

More About

Mean

Extended Capabilities

Tall ArraysCalculate with arrays that have more rows than fit in memory.

C/C++ Code GenerationGenerate C and C++ code using MATLAB® Coder™.

GPU Code GenerationGenerate CUDA® code for NVIDIA® GPUs using GPU Coder™.

Thread-Based EnvironmentRun code in the background using MATLAB®backgroundPoolor accelerate code with Parallel Computing Toolbox™ThreadPool.

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

Distributed ArraysPartition large arrays across the combined memory of your cluster using Parallel Computing Toolbox™.

版本历史

See Also

Mean Excluding`NaN`

`A`—Input array
vector|matrix|multidimensional array

`dim`—Dimension to operate along
positive integer scalar

`vecdim`—Vector of dimensions
vector of positive integers

`outtype`—Output data type
`'default'`(default) |`'double'`|`'native'`

`nanflag`—`NaN`condition
`“includenan”`(default) |`'omitnan'`

Tall Arrays
Calculate with arrays that have more rows than fit in memory.

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

GPU Code Generation
Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

Thread-Based Environment
Run code in the background using MATLAB®`backgroundPool`or accelerate code with Parallel Computing Toolbox™`ThreadPool`.

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

Distributed Arrays
Partition large arrays across the combined memory of your cluster using Parallel Computing Toolbox™.