speye - Sparse identity matrix - MATLAB (original) (raw)

Syntax

Description

[S](#mw%5Fba0101af-b06b-4993-bfe5-b5455d62eda3) = speye returns a sparse scalar1.

[S](#mw%5Fba0101af-b06b-4993-bfe5-b5455d62eda3) = speye([n](#mw%5Ffac7013e-940b-47c3-8d3f-e834dbc84f3e)) returns a sparse n-by-n identity matrix, with ones on the main diagonal and zeros elsewhere.

example

[S](#mw%5Fba0101af-b06b-4993-bfe5-b5455d62eda3) = speye([n](#mw%5Ffac7013e-940b-47c3-8d3f-e834dbc84f3e),[m](#mw%5Ffac7013e-940b-47c3-8d3f-e834dbc84f3e)) returns a sparse n-by-m matrix, with ones on the main diagonal and zeros elsewhere.

example

[S](#mw%5Fba0101af-b06b-4993-bfe5-b5455d62eda3) = speye([sz](#mw%5F84834ae2-7fa8-46f4-a47e-4f417c5028aa)) returns a matrix with ones on the main diagonal and zeros elsewhere. The size vectorsz defines size(S). For example, speye([2 3]) returns a 2-by-3 matrix.

example

[S](#mw%5Fba0101af-b06b-4993-bfe5-b5455d62eda3) = speye(___,[typename](#mw%5F34566fc1-cedf-4556-a6cb-92831bc3157e)) returns a sparse matrix of the specified data type. Specify the data type in addition to any of the input argument combinations in previous syntaxes. (since R2025a)

Examples

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Create a 1000-by-1000 square sparse identity matrix and view the sparsity pattern.

The result is the same as sparse(eye(1000)), but this latter version requires temporary storage for the full representation before it is converted to sparse storage.

Create a 400-by-800 sparse identity matrix and view the pattern of nonzeros.

S = speye(400,800); spy(S)

This command is equivalent to speye([400 800]).

Input Arguments

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Dimension sizes, specified as nonnegative integer scalars.

• If n is the only input argument, then S is an n-by-n identity matrix.
• If n or m is 0, thenS is an empty matrix.
• If n or m is negative, then it is treated as 0.

Example: speye(4) creates a 4-by-4 identity matrix.

Example: speye(3,6) creates a 3-by-6 identity matrix.

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

Since R2025a

Output data type, specified as "double","single", or "logical".

Dimension sizes, specified as a two-element row vector. The row vector is of the form [numRows numCols].

• If an element of sz is 0, thenS is an empty matrix.
• If an element of sz is negative, then the element is treated as 0.

Example: speye([4 5]) creates a 4-by-5 matrix and is equivalent tospeye(4,5).

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

Output Arguments

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Output matrix, returned as a sparse identity matrix.

Extended Capabilities

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The speye function supports GPU array input with these usage notes and limitations:

• To run this function on a GPU and obtain a gpuArray output, use any of these syntaxes:
  • S = gpuArray.speye.
  • S = gpuArray.speye(n).
  • S = gpuArray.speye(n,m).
  • S = gpuArray.speye(sz).
  • S = gpuArray.speye(___,typename), where typename specifies the data type in addition to the input argument combinations in any of the previous syntaxes. (since R2025a)

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

Version History

Introduced before R2006a

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You can specify the output data type by specifying the typename argument as "double", "single", or"logical".