sub2ind

Convert subscripts to linear indices

Syntax

ind = sub2ind(sz,row,col)

ind = sub2ind(sz,I1,I2,...,In)

Description

ind= sub2ind (sz,row,col)returns the linear indicesindcorresponding to the row and column subscripts inrowandcolfor a matrix of sizesz. Hereszis a vector with two elements, wheresz(1)specifies the number of rows andsz(2)specifies the number of columns.

example

ind= sub2ind (sz,I1,I2,...,In)returns the linear indicesindcorresponding to multidimensional subscripts innarraysI1,I2,...,Infor a multidimensional array of sizesz. Hereszis a vector withnelements that specifies the size of each array dimension.

Examples

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Convert Subscripts to Linear Indices for Matrix

Open Live Script

The mapping from subscripts (indexing by position) to linear indices for a 3-by-3 matrix can be illustrated as in the following.

Specify the row and column subscripts in a 3-by-3 matrix. Convert the subscripts to linear indices.

row = [1 2 3 1]; col = [2 2 2 3]; sz = [3 3]; ind = sub2ind(sz,row,col)

ind =1×44 5 6 7

Convert Subscripts to Linear Indices for Three-Dimensional Array

Open Live Script

The mapping from subscripts to linear indices for a 2-by-2-by-2 array can be illustrated as in the following.

Specify the row, column, and page subscripts in a 2-by-2-by-2 array. Convert the subscripts to linear indices.

I1 = [1 2 1 2]; I2 = [2 2 1 1]; I3 = [1 1 2 2]; sz = [2 2 2]; ind = sub2ind(sz,I1,I2,I3)

ind =1×43 4 5 6

Access Element of 3-D Array

Open Live Script

Convert a subscript index of a 3-D array to a single linear index.

Create an array, and find the linear index corresponding to the element in the (2,1,2) position.

A = rand(3,4,2); linearInd = sub2ind(size(A),2,1,2)

linearInd = 14

Check that both index versions refer to the same element.

A(2,1,2)

ans = 0.4854

A(14)

ans = 0.4854

Input Arguments

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`sz`—Size of array
vector of positive integers

Size of array, specified as a vector of positive integers. Each element of this vector indicates the size of the corresponding dimension. For example,[2 3 4]defines a 2-by-3-by-4 array.

`row`—Row subscripts
scalar|vector|matrix|multidimensional array

Row subscripts, specified as a scalar, vector, matrix, or multidimensional array. The size ofrowmust be the same as the size ofcol.

`col`—Column subscripts
scalar|vector|matrix|multidimensional array

Column subscripts, specified as a scalar, vector, matrix, or multidimensional array. The size ofcolmust be the same as the size ofrow.

`I1,I2,...,In`—Multidimensional subscripts
scalar|vector|matrix|multidimensional array

Multidimensional subscripts, specified as a scalar, vector, matrix, or multidimensional array. Each arrayI1,I2,…,Inmust have the same size.

Output Arguments

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`ind`— Linear indices
scalar | vector | matrix | multidimensional array

Linear indices, specified as a scalar, vector, matrix, or multidimensional array. The size ofindis the same as the size of the inputrow,col, orI1,I2,…,In.

Data Types:double

Algorithms

For an arrayA, ifind = sub2ind(size(A),I1,…,In), thenA(ind(k)) = A(I1(k),…,In(k))for allk.

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:

The first argument must be a valid size vector. Code generation does not support size vectors for arrays with more thanintmaxelements.
The generated code treatsNaNinputs as out of range and throws a run-time error.
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:

The first argument must be a valid size vector. Code generation does not support size vectors for arrays with more thanintmaxelements.

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™.

This function fully supports GPU arrays. 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™.

This function fully supports distributed arrays. For more information, seeRun MATLAB Functions with Distributed Arrays(Parallel Computing Toolbox).

中on History

Introduced before R2006a

sub2ind

Syntax

Description

Examples

Convert Subscripts to Linear Indices for Matrix

Convert Subscripts to Linear Indices for Three-Dimensional Array

Access Element of 3-D Array

Input Arguments

`sz`—Size of array
vector of positive integers

`row`—Row subscripts
scalar|vector|matrix|multidimensional array

`col`—Column subscripts
scalar|vector|matrix|multidimensional array

`I1,I2,...,In`—Multidimensional subscripts
scalar|vector|matrix|multidimensional array

Output Arguments

`ind`— Linear indices
scalar | vector | matrix | multidimensional array

Algorithms

Extended Capabilities

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™.

中on History

See Also

Topics

sub2ind

Syntax

Description

Examples

Convert Subscripts to Linear Indices for Matrix

Convert Subscripts to Linear Indices for Three-Dimensional Array

Access Element of 3-D Array

Input Arguments

sz—Size of arrayvector of positive integers

row—Row subscriptsscalar|vector|matrix|multidimensional array

col—Column subscriptsscalar|vector|matrix|multidimensional array

I1,I2,...,In—Multidimensional subscriptsscalar|vector|matrix|multidimensional array

Output Arguments

ind— Linear indicesscalar | vector | matrix | multidimensional array

Algorithms

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™.

中on History

See Also

Topics

`sz`—Size of array
vector of positive integers

`row`—Row subscripts
scalar|vector|matrix|multidimensional array

`col`—Column subscripts
scalar|vector|matrix|multidimensional array

`I1,I2,...,In`—Multidimensional subscripts
scalar|vector|matrix|multidimensional array

`ind`— Linear indices
scalar | vector | matrix | multidimensional array

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™.