diag

创建对角矩阵或对角线的元素matrix

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Syntax

d = diag（v)

d = diag（v，k）

x = diag（A)

x = diag（A,k)

Description

example

d = diag（v)returns a square diagonal matrix with the elements of vectorvon the main diagonal.

example

d = diag（v,k)places the elements of vectorvon thekth diagonal.k=0represents the main diagonal,K> 0is above the main diagonal, andk<0is below the main diagonal.

example

x = diag（A)返回主要对角线元件的列矢量A。

example

x = diag（A,k)returns a column vector of the elements on thekth diagonal ofA。

Examples

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创建对角线矩阵

打开实时脚本

Create a 1-by-5 vector.

V = [2 1 -1 -1 -2 -5];

利用diagto create a matrix with the elements ofvon the main diagonal.

d = diag（v)

d =5×52 0 0 0 0 0 0 0 0 0 0 0 0 0-1 0 0 0 0 0 0-2 0 0 0 0 0 0 -5

创建一个与元素的矩阵von the first super diagonal (k=1).

D1 =diag(v,1)

D1 =6×60 2 0 0 0 0 0 0 1 0 0 0 0 0 0 -1 0 0 0 0 0 0 -2 0 0 0 0 0 0 -5 0 0 0 0 0 0

这result is a 6-by-6 matrix. When you specify a vector of lengthn作为输入，diagreturns a square matrix of sizeN+ABS（K）。

获取对角线元素

打开实时脚本

Get the elements on the main diagonal of a random 6-by-6 matrix.

A = randi(10,6)

A =6×69 3 10 8 7 8 10 6 5 10 8 1 2 10 9 7 8 3 10 10 2 1 4 1 7 2 5 9 7 1 1 10 10 10 2 9

x = diag（A)

x =6×19 6 9 1 7 9

获取第一个分子的元素（k=-1) ofA。这result has one fewer element than the main diagonal.

x1 = diag(A,-1)

x1 =5×110 10 2 9 2

Callingdiag两次返回由原始矩阵的对角线元素组成的对角矩阵。

A1 = diag(diag(A))

A1 =6×69 0 0 0 0 0 0 6 0 0 0 0 0 0 9 0 0 0 0 0 0 1 0 0 0 0 0 0 7 0 0 0 0 0 0 9

Input Arguments

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`v`—Diagonal elements
vector

Diagonal elements, specified as a vector. Ifvis a vector withNelements, thendiag(v,k)is a square matrix of orderN+abs(k)。

diag([])returns an empty matrix,[]。

`A`—Input matrix
matrix

Input matrix.diag如果返回错误，如果ndims(A) > 2。

diag([])returns an empty matrix,[]。

`k`—Diagonal number
整数

Diagonal number, specified as an integer.k=0represents the main diagonal,K> 0is above the main diagonal, andk<0is below the main diagonal.

For anm-经过-nmatrix,k在范围内 $(- m + 1) \leq k \leq (n - 1)$ 。例如，对于与ngreater thanm, thek=0main diagonal consists of the elements with indices（1,1）,(2,2), ...,(m,m)。这k=1above the main diagonal consists of the elements with indices（1,2）,(2,3), ...,（m，m+1）。这k=-1在主角下方由带有指数的元素组成（2,1）,(3,2), ...,（M，M-1）。

Diagonal numbers k=0, k>0, and k<0

提示

这痕迹矩阵等于sum(diag(A))。

Extended Capabilities

C/C++ Code Generation
使用MATLAB®CODER™生成C和C ++代码。

Usage notes and limitations:

If you supplyk, then it must be a real and scalar integer value.
For variable-size inputs that are variable-length vectors (1-by-: or :-by-1),diag:
- Treats the input as a vector
- 返回沿指定对角线的输入向量的矩阵
For variable-size inputs that are not variable-length vectors,diag:
- Treats the input as a matrix
- Does not support inputs that are vectors at run time
- 返回可变长度向量
If the input is variable-size (:m-by-:n) and has shape 0-by-0 at run time, then the output is 0-by-1, not 0-by-0. However, if the input is a constant size 0-by-0, then the output is[]。
For variable-size inputs that are not variable-length vectors (1-by-: or :-by-1),diagtreats the input as a matrix from which to extract a diagonal vector. This behavior occurs even if the input array is a vector at run time. To forcediag要从不是1 by-的可变大小输入构建矩阵：或：-by-1，请使用：
- diag(x(:))instead ofdiag(x)
- diag(x(:),k)instead of诊断（x，k）
SeeVariable-Sizing Restrictions for Code Generation of Toolbox Functions(MATLAB Coder)。

GPU Code Generation
使用GPU CODER™为NVIDIA®GPU生成CUDA®代码。

Usage notes and limitations:

If you supplyk, then it must be a real and scalar integer value.
For variable-size inputs that are variable-length vectors (1-by-: or :-by-1),diag:
- Treats the input as a vector
- 返回沿指定对角线的输入向量的矩阵
For variable-size inputs that are not variable-length vectors,diag:
- Treats the input as a matrix
- Does not support inputs that are vectors at run time
- 返回可变长度向量
If the input is variable-size (:m-by-:n) and has shape 0-by-0 at run time, then the output is 0-by-1, not 0-by-0. However, if the input is a constant size 0-by-0, then the output is[]。
For variable-size inputs that are not variable-length vectors (1-by-: or :-by-1),diagtreats the input as a matrix from which to extract a diagonal vector. This behavior occurs even if the input array is a vector at run time. To forcediag要从不是1 by-的可变大小输入构建矩阵：或：-by-1，请使用：
- diag(x(:))instead ofdiag(x)
- diag(x(:),k)instead of诊断（x，k）

Thread-Based Environment
Run code in the background using MATLAB®`背景池`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
使用并行计算工具箱™在图形处理单元（GPU）上运行加速代码。

此功能完全支持GPU数组。金宝app有关更多信息，请参阅Run MATLAB Functions on a GPU(Parallel Computing Toolbox)。

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

此功能完全支持分布式数组。金宝app有关更多信息，请参阅运行具有分布式数组的MATLAB功能(Parallel Computing Toolbox)。

Version History

在R2006a之前引入

diag

Syntax

Description

Examples

创建对角线矩阵

获取对角线元素

Input Arguments

v—Diagonal elementsvector

A—Input matrixmatrix

k—Diagonal number整数

提示

Extended Capabilities

C/C++ Code Generation使用MATLAB®CODER™生成C和C ++代码。

GPU Code Generation使用GPU CODER™为NVIDIA®GPU生成CUDA®代码。

Thread-Based EnvironmentRun code in the background using MATLAB®背景池or accelerate code with Parallel Computing Toolbox™ThreadPool。

GPU Arrays使用并行计算工具箱™在图形处理单元（GPU）上运行加速代码。

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

Version History

See Also

`v`—Diagonal elements
vector

`A`—Input matrix
matrix

`k`—Diagonal number
整数

C/C++ Code Generation
使用MATLAB®CODER™生成C和C ++代码。

GPU Code Generation
使用GPU CODER™为NVIDIA®GPU生成CUDA®代码。

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

GPU Arrays
使用并行计算工具箱™在图形处理单元（GPU）上运行加速代码。

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