spy

Visualize sparsity pattern of a sparse model

Syntax

spy(sys)

spy(parent,sys)

Description

spy(sys) plots the sparsity pattern of the sparse model sys, which can be a first-order (sparss) or second-order (mechss) model. The plot displays the number of nonzero elements in each sparse matrix of sys. To display a matrix, right click the plot and select the desired matrix.

spy(parent,sys) in the specified parent graphics container, such as a Figure or TiledChartLayout. Use this syntax when you want to create a plot in a specified open figure or when creating apps in App Designer.

Examples

Continuous-Time Sparse First-Order Model

For this example, consider sparseFOContinuous.mat which contains sparse matrices for a continuous-time sparse first-order state-space model.

Extract the sparse matrices from sparseFOContinuous.mat.

load('sparseFOContinuous.mat','A','B','C','D','E');

Create the sparss model object.

sys = sparss(A,B,C,D,E)

Sparse continuous-time state-space model with 1 outputs, 1 inputs, and 199 states.
Model Properties

Use "spy" and "showStateInfo" to inspect model structure. 
Type "help sparssOptions" for available solver options for this model.

The output sys is a continuous-time sparss model object with 199 states, 1 input and 1 output.

You can use the spy command to visualize the sparsity of the sparss model object.

spy(sys)

Discrete-Time Sparse First-Order Model

For this example, consider sparseFODiscrete.mat which contains sparse matrices for a discrete-time sparse first-order state-space model.

Extract the sparse matrices from sparseFODiscrete.mat.

load('sparseFODiscrete.mat','A','B','C','D','E','ts');

Create the sparss model object.

sys = sparss(A,B,C,D,E,ts)

Sparse discrete-time state-space model with 1 outputs, 1 inputs, and 398 states.
Model Properties

Use "spy" and "showStateInfo" to inspect model structure. 
Type "help sparssOptions" for available solver options for this model.

The output sys is a discrete-time sparss model object with 398 states, 1 input and 1 output.

You can use the spy command to visualize the sparsity of the sparss model object.

spy(sys)

You can also view model properties of the sparss model object.

properties('sparss')

Properties for class sparss:

    A
    B
    C
    D
    E
    Offsets
    Scaled
    StateInfo
    SolverOptions
    InternalDelay
    InputDelay
    OutputDelay
    InputName
    InputUnit
    InputGroup
    OutputName
    OutputUnit
    OutputGroup
    Notes
    UserData
    Name
    Ts
    TimeUnit
    SamplingGrid

Continuous-Time Sparse Second-Order Model

For this example, consider the sparse matrices for the 3-D beam model subjected to an impulsive point load at its tip in the file sparseBeam.mat.

Extract the sparse matrices from sparseBeam.mat.

load('sparseBeam.mat','M','K','B','F','G','D');

Create the mechss model object by specifying [] for matrix C, since there is no damping.

sys = mechss(M,[],K,B,F,G,D)

Sparse continuous-time second-order model with 3 outputs, 1 inputs, and 3408 degrees of freedom.
Model Properties

Use "spy" and "showStateInfo" to inspect model structure. 
Type "help mechssOptions" for available solver options for this model.

The output sys is a mechss model object containing a 3-by-1 array of sparse models with 3408 degrees of freedom, 1 input, and 3 outputs.

You can use the spy command to visualize the sparsity of the mechss model object.

spy(sys)

Discrete-Time Sparse Second-Order Model

For this example, consider the sparse matrices of the discrete system in the file discreteSOSparse.mat.

Load the sparse matrices from discreteSOSparse.mat.

load('discreteSOSparse.mat','M','C','K','B','F','G','D','ts');

Create the discrete-time mechss model object by specifying the sample time ts.

sys = mechss(M,C,K,B,F,G,D,ts)

Sparse discrete-time second-order model with 1 outputs, 1 inputs, and 28408 degrees of freedom.
Model Properties

Use "spy" and "showStateInfo" to inspect model structure. 
Type "help mechssOptions" for available solver options for this model.

The output sys is a discrete-time mechss model object with 28408 degrees of freedom, 1 input, and 1 output.

You can use the spy command to visualize the sparsity pattern of the mechss model object. You can right-click on the plot to select matrices to be displayed.

spy(sys)

Input Arguments

sys — Sparse model

sparss object | mechss object

Sparse model, specified as a one of the following objects.

• sparss — First-order sparse model

• mechss — Second-order sparse model

When sys contains interfaced or interconnected components, use spy(xsort(sys)) to view the underlying block arrow structure. For more information about the block arrow structure, see xsort.

parent — Parent graphics container

Figure object | TiledChartLayout object | UIFigure object | UIGridLayout object | UIPanel object | UITab object | Axes object | UIAxes object

Parent graphics container, specified as one of these objects:

• Figure

• TiledChartLayout

• UIFigure

• UIGridLayout

• UIPanel

• UITab

You can also specify parent as an Axes or UIAxes object, which sets the plot parent to the parent of the specified axes object.

Version History

Introduced in R2020b

R2025a: Specify parent graphics container other than axes

You can now plot the sparsity pattern of a sparse model in a parent container other than an axes. To do so, specify the parent argument as a graphics container, such as a Figure or TiledChartLayout object. Specifying an Axes or UIAxes object is still supported.