Programmatic Modeling Basics

You can perform most Simulink^® modeling basics programmatically at the MATLAB^® Command Window, such as creating models, adding blocks to models, and setting parameters. These examples show some of these commands and how you can use them.

Load a Model

Loading a model brings it into memory but does not open it in the Simulink Editor for editing. After you load a model, you can work with it programmatically. You can use the Simulink Editor to edit the model only if you open the model.

To load a system, use the load_system command.

For example, suppose you have a model named myModel on the MATLAB path. To load the model, enter this command in the MATLAB Command Window:

load_system('myModel')

Create a Model and Specify Parameter Settings

You can write a function that creates a model and uses the settings that you prefer. For example, this function creates a model that has a green background and uses the ode3 solver:

function new_model(modelname) 
% NEW_MODEL Create a new, empty Simulink model
%    NEW_MODEL('MODELNAME') creates a new model with
%    the name 'MODELNAME'. Without the 'MODELNAME'
%    argument, the new model is named 'my_untitled'.

if nargin == 0 
     modelname = 'my_untitled';
end 

% create and open the model
open_system(new_system(modelname));

% set default screen color
set_param(modelname,'ScreenColor','green');

% set default solver
set_param(modelname,'Solver','ode3');

% save the model
save_system(modelname);

Programmatically Load Variables When Opening a Model

If you assign a variable as a block parameter value, you must define the value of the variable in the model. You can define the variable programmatically using the PreloadFcn callback with the set_param function. Use the function in this form:

set_param('mymodel','PreloadFcn','expression')

expression is a MATLAB command or a MATLAB script on your MATLAB search path. This command sets the model PreloadFcn callback to the value that you specify. Save the model to save the setting.

For example, when you define the variables in a MATLAB script loadvar.m for the model modelname.slx, use this command:

set_param('modelname','PreloadFcn','loadvar')

To assign the variable K the value 15, use this command:

set_param('modelname','PreloadFcn','K=15')

After you save the model, the PreloadFcn callback executes when you next open the model.

Programmatically Add and Connect Blocks

This example shows how to use functions to add blocks and connect the blocks programmatically.

Create and open a blank model named "mymodel".

new_system('mymodel');
open_system('mymodel');

Add blocks using the add_block function.

sine1 = 'mymodel/Sine1';
pulse1 = 'mymodel/Pulse1';
subsystem1 = 'mymodel/Subsystem1';
scope1 = 'mymodel/Scope1';

add_block('simulink/Sources/Sine Wave',sine1);
add_block('simulink/Sources/Pulse Generator',pulse1);
add_block('simulink/Ports & Subsystems/Subsystem',subsystem1);
add_block('simulink/Sinks/Scope',scope1);

Make the block names always visible.

set_param('mymodel',HideAutomaticNames="off");

Delete the contents of Subsystem1.

Simulink.SubSystem.deleteContents('mymodel/Subsystem1');

Insert an Add block inside Subsystem1.

add1 = 'mymodel/Subsystem1/Add1';
add_block('simulink/Math Operations/Add',add1);

Next, add lines to connect all the blocks in the model. Start by connecting Add1 to Scope1 using the Simulink.connectBlocks function. Since there is only one possible way to connect these two blocks, you do not need to specify which ports to connect in the function input arguments. Instead, you can simply specify the block path.

Simulink.connectBlocks(add1,scope1)

Connect Sine1 to the top input port of Add1. To connect specific ports, you must specify which ports to connect in the function input arguments. Get the handles of the ports you want to connect. For each block, use the get_param function to get the handles of all ports on the block. Then, use dot notation and the port name to extract the handle of the port you want to connect.

allPortsSine = get_param(sine1,'PortHandles')
srcPort = allPortsSine.Outport

allPortsAdd = get_param(add1,'PortHandles')
dstPort = allPortsAdd.Inport(1)

Simulink.connectBlocks(srcPort,dstPort);

Use the same approach to connect Pulse1 to the bottom input port of Add1.

allPortsPulse = get_param(pulse1,'PortHandles');
srcPort = allPortsPulse.Outport;

dstPort = allPortsAdd.Inport(2);

Simulink.connectBlocks(srcPort,dstPort);

Auto-arrange the model.

Simulink.BlockDiagram.arrangeSystem('mymodel')

Auto-arrange the subsystem.

Simulink.BlockDiagram.arrangeSystem('mymodel/Subsystem1')

Programmatically Comment Out or Comment Through Blocks

To view or change the commented state of a block programmatically, use the get_param and set_param commands.

To view the commented state of a block:
get_param(gcb,'commented');
To comment out a block:
set_param(gcb,'commented','on');
To comment through a block:
set_param(gcb,'commented','through');
To uncomment a block:
set_param(gcb,'commented','off');

Name a Signal Programmatically

Select the block whose output port connects to the signal line.
Use get_param to assign the port handle of the currently selected block to the variable p. Use get_param to assign the handle of the line connected to that port to the variable l. Then set the name of the signal line to 's9'.

p = get_param(gcb,'PortHandles')
l = get_param(p.Outport,'Line')
set_param(l,'Name','s9')

Arrange Model Layouts Automatically

You can use the Simulink.BlockDiagram.arrangeSystem command to lay out your model. This command aligns input blocks on the left, output blocks on the right, and model elements in columns between the inputs and outputs. The command affects only one layer at a time.

You can use the Simulink.BlockDiagram.routeLine command to route existing lines of your model. Routing existing lines improves line route quality and avoids overlaps of a line with other lines and obstacles in the model.

While you can use these commands with any open model, they are particularly useful with models you build programmatically. For an example, see Arrange Programmatically Populated Model.

Open the Same Model in Multiple Windows

When you open a model, the model appears in a Simulink Editor window. For example, if you have one model open and then you open a second model, the second model appears in a second window.

To open the same model in two Simulink Editor windows, at the MATLAB command prompt, enter the open_system command and use the window argument. For example, if you have a model called modelName open, to open another instance of modelName, enter:

open_system('modelName','window')

Use Model Finder to Index and Search Models and Improve Their Discoverability

You can use the modelfinder function to search examples, models, and projects in multiple databases. By default, modelfinder searches the MathWorks^® Examples database. You can also configure your databases with Model Finder. For more information on Model Finder, see Configure, Share, and Search Databases.

Locate Diagram Elements Using Highlighting

To highlight a block, line, port, or annotation in an open model, use hilite_system.

Specify Colors Programmatically

You can use the set_param command at the MATLAB command line or in a MATLAB program to set parameters that determine the background color of a diagram and the background color and foreground color of diagram elements. The following table summarizes the parameters that control model colors.

Parameter	Determines
`ScreenColor`	Model background
`BackgroundColor`	Block and annotation background
`ForegroundColor`	Block and annotation foreground

Set the color parameter to either a named color or an RGB value.

Named color: 'automatic', 'black', 'white', 'red', 'green', 'blue', 'cyan', 'magenta', 'yellow', 'gray', 'lightBlue', 'orange', 'darkGreen'
RGB value: '[r,g,b]'
where r, g, and b are the red, green, and blue components of the color normalized to the range 0.0 to 1.0.

For example, the following command sets the background color of the currently selected system or subsystem to a light green color:

set_param(gcs,'ScreenColor','[0.3, 0.9, 0.5]')