sim

R2026b

Run and script programmatic simulations of Simulink models

Syntax

out = sim(simin)

out = sim(simin,Name=Value)

out = sim(mdl)

out = sim(mdl,Name=Value)

out = sim(mdl,params)

out = sim(mdl,configset)

Description

Simulink.SimulationInput Object Syntax

out = sim(simin) runs one or more simulations of a Simulink^® model according to the properties defined on one or more Simulink.SimulationInput objects.

• If simin is a scalar Simulink.SimulationInput object, then out is a scalar Simulink.SimulationOutput object.

• If simin is a vector, matrix, or array of Simulink.SimulationInput objects, then out is a vector, matrix, or array of Simulink.SimulationOutput objects with the same dimensions as simin.

You can use a Simulink.SimulationInput object to configure options and inputs for simulations, including:

• The model to simulate

• Source variables or files for external input data

• Block parameter values to use for the simulation

• Model configuration parameter values to use for the simulation

When a property of the Simulink.SimulationInput object modifies a model or block parameter value, the value is modified during simulation and reverted at the end of the simulation.

When you configure programmatic simulations using Simulink.SimulationInput objects, you can transition from using the sim function to using other functions, such as parsim and batchsim.

For more information, see Run Simulations Programmatically.

out = sim(simin,Name=Value) runs the simulations with additional options specified using one or more name-value arguments.

For a list of name-value arguments supported by the Simulink.SimulationInput syntax, see Simulink.SimulationInput Object Syntax.

Model Syntax

out = sim(mdl) simulates the model mdl using the current configuration parameter and block parameter values specified in the model.

• If the model has the Single simulation output parameter or fast restart enabled, out is a Simulink.SimulationOutput object.

• If the model does not have Single simulation output or fast restart enabled, out is a vector that contains the simulation times. For more information, see Syntaxes that return multiple output arguments are not recommended.

out = sim(mdl,Name=Value) simulates the model with options specified using one or more name-value arguments. For example, you can modify a model configuration parameter value for the simulation by specifying the parameter name and value as a name-value argument.

When you modify model configuration parameters by providing inputs to the sim function, the changes are applied during simulation and reverted at the end of the simulation.

For a list of name-value arguments supported for the model syntax, see Model Syntax.

out = sim(mdl,params) simulates the model using the model configuration parameter values specified by the structure params.

out = sim(mdl,configset) simulates the model using model configuration parameter values in the configuration set configset.

Examples

Run Simulations Using Current Parameter Values

Suppose you have a model named IntegrateSine that integrates the output of a Sine Wave block and logs the result using an Outport block. A Scope block displays the sine wave input and the integrated output. You open the model and want to simulate the model using the parameter values saved in the model.

Simulate the model by specifying the name of the model as input to the sim function.

out = sim(mdl);

The simulation runs using the current model configuration parameters and block parameters specified in the model. In this case, the model has a stop time of 10 seconds, and the amplitude of the Sine Wave block is 1.

Specify Variable Values and Model Parameters for Simulation Using Simulink.SimulationInput Objects

To modify parameters in a model for simulation without dirtying the model, use a Simulink.SimulationInput object to configure the simulation. When you configure simulations using Simulink.SimulationInput objects, you can configure model configuration parameter, block parameter, and variable values. The sim function applies the configuration specified on the Simulink.SimulationInput object during the simulation and reverts changes to the model when the simulation completes.

Suppose you want to simulate the model IntegrateSine described in Run Simulations Using Current Parameter Values for different amplitudes of the sine wave input.

To parameterize the model, specify the value of the Sine Wave block Amplitude parameter as a variable. Open the model. Then, define the variable in the base workspace and specify the value of the block parameter in the model as the variable.

mdl = "IntegrateSine";
open_system(mdl)
a = 1;
set_param(mdl + "/Sine Wave",Amplitude="a")

Create a Simulink.SimulationInput object to store the simulation configuration. Specify parameter and variable values on the Simulink.SimulationInput object to configure a simulation that:

• Uses the solver ode45

• Runs through a stop time of 20 seconds

• Sets the amplitude of the simulated sine wave input to 2

mdl = "IntegrateSine";
simin = Simulink.SimulationInput(mdl);
simin = setModelParameter(simin,Solver="ode45",StopTime="20");
simin = setVariable(simin,"a",2);

Simulate the model by specifying the Simulink.SimulationInput object as input to the sim function.

out = sim(simin);

The model simulates for 20 seconds, using the solver ode45 and a sine wave amplitude of 2.

After the simulation completes, the variable in the workspace, the solver parameter, and the stop time parameter revert to their original values.

Speed Up Parameter Sweeps by Using Fast Restart

Fast restart speeds up parameter sweeps by compiling the model only once, before the execution phase of the first simulation. Each subsequent simulation reinitializes the model with specified parameter values without recompiling the model, which can significantly reduce the overall time required to run the parameter sweep. To enable fast restart for parameter sweeps run using a single call to the sim function, specify the UseFastRestart name-value argument as "on".

Suppose you want to simulate the model IntegrateSine described in Run Simulations Using Current Parameter Values for different amplitudes of the sine wave input.

To parameterize the model, specify the value of the Sine Wave block Amplitude parameter as a variable. Open the model. Then, define the variable in the base workspace and specify the value of the block parameter in the model as the variable.

mdl = "IntegrateSine";
open_system(mdl)
a = 1;
set_param(mdl + "/Sine Wave",Amplitude="a")

Create a vector of the parameter values you want to simulate. Then, create an array of Simulink.SimulationInput objects that represent the configuration for each simulation in the parameter sweep. In a for loop, specify the value of the variable that defines the parameter on each Simulink.SimulationInput object.

mdl = "IntegrateSine";
amps = [1 2 3 4 5 6];
n = length(amps);
simin(1:n) = Simulink.SimulationInput(mdl);

for k = n:-1:1
    simin(k) = setVariable(simin(k),"a",amps(k));
end

Run the parameter sweep using a single call to the sim function that enables fast restart by specifying the UseFastRestart name-value argument as "on".

out = sim(simin,UseFastRestart="on");

[14-Apr-2026 17:31:23] Running simulations...
[14-Apr-2026 17:31:24] Completed 1 of 6 simulation runs
[14-Apr-2026 17:31:25] Completed 2 of 6 simulation runs
[14-Apr-2026 17:31:25] Completed 3 of 6 simulation runs
[14-Apr-2026 17:31:25] Completed 4 of 6 simulation runs
[14-Apr-2026 17:31:26] Completed 5 of 6 simulation runs
[14-Apr-2026 17:31:26] Completed 6 of 6 simulation runs

The sim function returns the simulation results as an array of Simulink.SimulationOutput objects. Each Simulink.SimulationOutput object in the array contains the results for the simulation configured using the Simulink.SimulationInput object with the same index in the input array. For example, the Simulink.SimulationOutput object at index 1 in the output array contains the results for the simulation run using the Simulink.SimulationInput object at index 1 in the input array.

Access the output data logged in the first simulation, which used an amplitude of 1.

yout1 = out(1).yout

yout1 = 
Simulink.SimulationData.Dataset 'yout' with 1 element

                         Name    BlockPath             
                         ______  _____________________ 
    1  [1x1 Signal]      output  IntegrateSine/Outport

  - Use braces { } to access, modify, or add elements using index.

To suppress the progress messages, specify the ShowProgress name-value argument as "off". To monitor progress using the Simulation Manager, specify the ShowSimulationManager name-value argument as "on". For more information, see Simulation Manager.

Specify Model Parameters for Simulation Using Name-Value Arguments

To configure simulations without dirtying the model, you can specify one or more name-value arguments. The sim function modifies the parameters during simulation and reverts changes to the model when the simulation completes. Name-value arguments can specify only model configuration parameters. To configure additional parameters, such as variable and block parameter values, use a Simulink.SimulationInput object instead.

Suppose you want to simulate the model IntegrateSine, described in Run Simulations Using Current Parameter Values, for 20 seconds using the solver ode45.

Simulate the model. Specify the Stop time and Solver parameters for the simulation using name-value arguments.

mdl = "IntegrateSine";
out = sim(mdl,StopTime="20",Solver="ode45");

To see the parameter values used in the simulation, check the simulation metadata returned with the simulation results.

slvr = out.SimulationMetadata.ModelInfo.SolverInfo.Solver

slvr =

    'ode45'

tstop = out.SimulationMetadata.ModelInfo.StopTime

tstop =

    20

Specify Model Parameters for Simulation Using Structure

To configure simulations without dirtying the model, you can specify a structure that defines the name and value of each parameter you want to modify. The sim function modifies the specified parameters during simulation and reverts changes to the model when the simulation completes. The structure can specify only model configuration parameters. To configure additional parameters, such as variable and block parameter values, use a Simulink.SimulationInput object instead.

Suppose you want to simulate the model IntegrateSine, described in Run Simulations Using Current Parameter Values, for 20 seconds using the solver ode45.

Create a structure that contains the fields Solver and StopTime.

simconfig.Solver = "ode45";
simconfig.StopTime = "20";

Simulate the model using the parameter values specified in the structure.

mdl = "IntegrateSine";
out = sim(mdl,simconfig);

To see the parameter values used in the simulation, check the simulation metadata returned with the simulation results.

slvr = out.SimulationMetadata.ModelInfo.SolverInfo.Solver

slvr =

    'ode45'

tstop = out.SimulationMetadata.ModelInfo.StopTime

tstop =

    20

Specify Configuration Set for Simulation

To apply a configuration set to a simulation without dirtying the model, configure the simulation using a Simulink.ConfigSet object. The sim function applies the configuration set to the model during simulation and reverts the change when the simulation completes. A configuration set specifies only model configuration parameter values. To specify additional values, such as variable and block parameter values, use a Simulink.SimulationInput object instead.

Suppose you want to simulate the model IntegrateSine, described in Run Simulations Using Current Parameter Values, for 20 seconds using the solver ode45.

To specify the parameter values to use in the simulation, create and configure a Simulink.ConfigSet object. Open the model and get the current configuration set. Then, create a copy of the configuration set and specify the stop time and solver on the copy.

mdl = "IntegrateSine";
open_system(mdl)
mdlconfig = getActiveConfigSet(mdl);
simconfig = copy(mdlconfig);
set_param(simconfig,StopTime="20");
set_param(simconfig,Solver="ode45");

Simulate the model using the configuration set simconfig.

out = sim(mdl,simconfig);

To see the parameter values used in the simulation, check the simulation metadata returned with the simulation results.

slvr = out.SimulationMetadata.ModelInfo.SolverInfo.Solver

slvr =

    'ode45'

tstop = out.SimulationMetadata.ModelInfo.StopTime

tstop =

    20

Input Arguments

simin — Simulation inputs and configuration

Simulink.SimulationInput object | array of Simulink.SimulationInput objects

Simulation inputs and configuration, specified as a Simulink.SimulationInput object or an array of Simulink.SimulationInput objects. The properties of the Simulink.SimulationInput object specify options and parameter values to use in the simulation, including:

• The model to simulate

• Source variables or files for external input data

• Block parameter values to use for the simulation

• Model configuration parameter values to use for the simulation

The values defined in the properties of the Simulink.SimulationInput object are applied to the model for the simulation and reverted at the end of simulation.

mdl — Model to simulate

string | character vector | model handle

Model to simulate, specified as a string or a character vector that defines the name of the model or as a model handle (since R2024a).

Example: out = sim("vdp") simulates the model named vdp using the parameter values currently configured in the model.

Data Types: char | string

params — Model parameter values to use in simulation

structure

Model parameter values to use in simulation, specified as a structure. To specify a parameter value, add a field to the structure that matches the programmatic name of the model parameter. For example, to specify a start time of 5 seconds and a stop time of 10 seconds, create this structure:

params.StartTime = "5";
params.StopTime = "10";

Data Types: struct

configset — Configuration set to use in simulation

Simulink.ConfigSet object

Configuration set to use in simulation, specified as a Simulink.ConfigSet object.

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Example: out = sim(simin,UseFastRestart="on") runs a set of simulations using fast restart.

Example: out = sim(mdl,FastRestart="on") enables fast restart and runs a simulation of the model mdl.

Note

The sim function supports different name-value arguments depending on whether you specify the first input as one or more Simulink.SimulationInput objects or as the name or handle of the model to simulate.

Simulink.SimulationInput Object Syntax

UseFastRestart — Option to enable fast restart

"off" (default) | "on"

Option to enable fast restart, specified as "off" or "on". Fast restart reduces the time required to run a set of simulations by compiling the model only once, before the execution phase of the first simulation. For more information, see How Fast Restart Improves Iterative Simulations.

Consider using fast restart when you run multiple simulations of a model by specifying an array of Simulink.SimulationInput objects. For more information, see Script Iterative or Batch Simulations Using Fast Restart.

This argument is supported only when you specify the first input to the sim function as one or more Simulink.SimulationInput objects.

This argument has no effect when you specify a scalar Simulink.SimulationInput object. To enable fast restart, specify the FastRestart parameter on the Simulink.SimulationInput object using the setModelParameter function. When you enable fast restart using a scalar Simulink.SimulationInput object, fast restart remains enabled in the model after the simulation completes.

Example: out = sim(simin,UseFastRestart="on");

Data Types: char | string

StopOnError — Option to skip subsequent simulations if simulation error occurs

"off" (default) | "on"

Option to skip subsequent simulations if simulation error occurs, specified as "off" or "on".

• "off" — If a simulation error occurs, the software captures the error in the simulation output and continues to run any subsequent simulations.

  For example, suppose you run five simulations using an array of Simulink.SimulationInput objects. An error occurs during the second simulation. The sim function captures the error in the output for the second simulation and continues to run the third, fourth, and fifth simulations.

• "on" — If a simulation error occurs, the software captures the error in the simulation output and does not run any subsequent simulations.

  For example, suppose you run five simulations using an array of five Simulink.SimulationInput objects. An error occurs during the second simulation. The software captures the error in the output for the second simulation and does not run the third, fourth, and fifth simulations. The sim function returns an empty Simulink.SimulationOutput object for each simulation that does not run.

This argument has no effect when you specify the first input to the sim function as a scalar Simulink.SimulationInput object. (since R2024a)

This argument is supported only when you specify the first input to the sim function as one or more Simulink.SimulationInput objects.

Example: out = sim(simin,StopOnError="on");

Tips

• When the first input is an array of Simulink.SimulationInput objects, the sim function always enables CaptureErrors for each simulation.

• View information about captured errors in the simulation output and metadata.

  • The sim function captures the error in the ErrorMessage property of the Simulink.SimulationOutput object.

    msg = out.ErrorMessage;

  • To view the error message in the Diagnostic Viewer, use the sldiagviewer.reportSimulationMetadataDiagnostics function.

    sldiagviewer.reportSimulationMetadataDiagnostics(out)

  • The Simulink.SimulationMetadata object returned by the simulation contains additional information about the error, such as the simulation phase in which the error occurred. The error information is stored in the ErrorDiagnostic field of the ExecutionInfo property.

    e = out.SimulationMetadata.ExecutionInfo.ErrorDiagnostic;

Data Types: char | string

ShowProgress — Option to indicate simulation progress

"off" | "on"

Option to indicate simulation progress, specified as "off" or "on".

• "off" — Simulations run without displaying progress messages.

• "on" — Progress updates are displayed as simulations run.

The default value for this parameter depends on the dimensions of the first input to the sim function:

• When the first input is a scalar Simulink.SimulationInput object, the default value is "off".

• When the first input is an array of Simulink.SimulationInput objects, the default value is "on".

This argument is supported only when you specify the first input to the sim function as one or more Simulink.SimulationInput objects.

Example: out = sim(simin,ShowProgress="on");

ShowSimulationManager — Option to monitor progress using Simulation Manager

"off" (default) | "on"

Option to monitor progress using Simulation Manager, specified as "off" or "on". Consider using the Simulation Manager when you run multiple simulations using a single call to the sim function.

This argument is supported only when you specify the first input to the sim function as one or more Simulink.SimulationInput objects.

Example: out = sim(simin,ShowSimulationManager="on");

Model Syntax

Configuration Parameter Name — Model configuration parameter value to use in simulation

configuration parameter value

Model configuration parameter value to use in simulation, specified as a name-value argument that consists of the programmatic name of the configuration parameter and the parameter value.

For example, to configure the Stop time parameter, specify the name-value argument using the name StopTime and the parameter value. These commands run a 100-second simulation of a model named MyModel.

mdl = "MyModel";
out = sim(mdl,StopTime="100");

You can use a name-value argument to specify the value for any model configuration parameter in simulations you run using the sim function. The configuration parameter values you specify are applied for the simulation and revert when the simulation ends. When you simulate a model hierarchy, the configuration parameter values you specify apply to the top model.

Specifying model configuration parameter values as name-value arguments is supported only when you specify the first input to the sim function as the name or handle of the model to simulate.

Example: out = sim("MyModel",SaveOutput="on");

Tips

• To specify configuration parameter values on a Simulink.SimulationInput object, use the setModelParameter function.

  simin = Simulink.SimulationInput("MyModel");
  simin = setModelParameter(simin,StopTime="100");

• To get a list of model configuration parameters, use the getActiveConfigSet function and the get_param function.

  configSet = getActiveConfigSet("vdp");
  configSetNames = get_param(configSet,"ObjectParameters")

  The get_param function returns a list of all the model configuration parameters, such as StopTime, SaveTime, SaveState, SaveOutput, and SignalLogging.

FastRestart — Option to enable fast restart for individual simulations

"off" | "on"

Option to enable fast restart for individual simulations, specified as "on" or "off". Fast restart saves time in iterative simulation workflows by skipping compilation and termination after compiling the model for the first simulation you run after enabling fast restart.

• "on" — The simulation enables the FastRestart parameter in the model and runs using fast restart. After the simulation ends, the FastRestart parameter remains enabled in the model.

  If the model is not already initialized in fast restart, the software compiles the model before running the simulation. At the end of the simulation, the model remains initialized in fast restart. To terminate the simulation, disable fast restart. For more information, see Script Iterative or Batch Simulations Using Fast Restart.

• "off" — The simulation disables the FastRestart parameter in the model and runs without using fast restart. The model compiles for each simulation.

  If the model is already initialized in fast restart, the sim function terminates the previous simulation before compiling the model.

By default, fast restart is disabled in models, and simulations you run using the sim function do not enable fast restart. If you do not specify this argument, the sim function uses the value of the parameter in the model.

This argument is supported only when you specify the first input to the sim function as a model name or handle.

Example: out = sim("MyModel",FastRestart="on");

Tips

• To specify this parameter on a Simulink.SimulationInput object, use the setModelParameter function. (since R2024a)

  simin = Simulink.SimulationInput("MyModel");
  simin = setModelParameter(simin,FastRestart="on");

• To run a set of simulations using fast restart, specify the first input argument as an array of Simulink.SimulationInput objects and use the UseFastRestart name-value argument instead.

• If you enable fast restart using the Simulink Editor or the set_param function, simulations you run using the sim function use fast restart even if you do not specify this argument.

• Fast restart simulations return results as a single Simulink.SimulationOutput object, even if the Single simulation output configuration parameter is disabled.

Data Types: char | string

SimulationMode — Simulation mode

"normal" | "accelerator" | "rapid-accelerator"

Simulation mode, specified as "normal", "accelerator", or "rapid-accelerator". If you do not specify this argument, the simulation uses the simulation mode specified in the model.

Value	Description
"normal"	Run simulation using normal mode. Normal mode simulations use the full model representation and provide the best support for interacting with the model during simulation. Use normal mode for workflows that involve modifying the structure of your model between simulations. For best results, use normal mode for debugging simulations.
"accelerator"	Run simulation using accelerator mode. Accelerator mode simulations generate an optimized representation of the model, called a simulation target, to use in simulation. The optimizations that improve the simulation performance can reduce the ability to interact with the model during simulation. Modifying the model between accelerator mode simulations can require regenerating the simulation target. Use accelerator mode to speed up simulations in workflows that do not involve making structural changes to the model between simulations.
"rapid-accelerator"	Run simulation using rapid accelerator mode. Rapid accelerator mode simulations generate a simulation target to use for simulation. The simulation target provides minimal support for interacting with the model during simulation. Modifying the model between rapid accelerator simulations can require rebuilding the simulation target. Use rapid accelerator mode for the fastest simulation execution when you modify the model between simulations only by tuning variable and parameter values. Tuning certain parameter values can require rebuilding the simulation target.

For more information, see Choosing a Simulation Mode and Code Regeneration in Accelerated Models.

This argument is supported only when you specify the first input to the sim function as a model name or handle.

Example: out = sim("MyModel",SimulationMode="accelerator");

Tips

• To specify the simulation mode on a Simulink.SimulationInput object, use the setModelParameter function.

  simin = Simulink.SimulationInput("MyModel");
  simin = setModelParameter(simin,SimulationMode="accelerator");

• Visualization blocks update during simulation when you run simulations from a UI, such as the Simulink Editor, but do not update during simulation when you run rapid accelerator simulations programmatically.

• To prevent rebuilding the simulation target, you can disable the rapid accelerator up-to-date check by specifying the RapidAcceleratorUpToDateCheck parameter value as "off". With the up-to-date check disabled, changes you make that would require rebuilding the simulation target are ignored.

• To simulate using rapid accelerator mode, you can specify "rapid" as a partial match for "rapid-accelerator". For more information about name-value arguments in MATLAB^®, see Validate Name-Value Arguments.

Data Types: char | string

CaptureErrors — Option to capture errors and return simulation output if simulation error occurs

"off" (default) | "on"

Option to capture errors and return simulation output if simulation error occurs, specified as "off" or "on".

Behavior	CaptureErrors="off" (default)	CaptureErrors="on"
Issuing exceptions for simulation errors	The software issues exceptions for simulation errors. The exception stops both the simulation in which the error occurred and the script or function that invoked the simulation, if applicable.	The software does not issue exceptions for simulation errors. If a script or another function invoked the simulation, the error stops the simulation but does not stop the execution of the script or function.
Error reporting	Errors that occur during simulation are reported in the MATLAB Command Window.	Information about the simulation errors, including the message and the simulation phase in which the error occurred, is captured in the simulation output.
Simulation results	Issuing an exception stops the simulation immediately. The sim function does not return simulation results.	The sim function returns simulation results and metadata up to the simulation time at which the error occurred.

This argument is supported only when you specify the first input to the sim function as a model name or handle.

Example: out = sim("MyModel",CaptureErrors="on");

Tips

• This option is not supported for software-in-the-loop (SIL) and processor-in-the-loop (PIL) simulations.

• To specify this parameter on a Simulink.SimulationInput object, use the setModelParameter function. (since R2024a)

  simin = Simulink.SimulationInput("MyModel");
  simin = setModelParameter(simin,CaptureErrors="on");

• View information about captured errors in the simulation output and metadata.

  • The sim function captures the error in the ErrorMessage property of the Simulink.SimulationOutput object.

    msg = out.ErrorMessage;

  • To view the error message in the Diagnostic Viewer, use the sldiagviewer.reportSimulationMetadataDiagnostics function.

    sldiagviewer.reportSimulationMetadataDiagnostics(out)

  • The Simulink.SimulationMetadata object returned by the simulation contains additional information about the error, such as the simulation phase in which the error occurred. The error information is stored in the ErrorDiagnostic field of the ExecutionInfo property.

    e = out.SimulationMetadata.ExecutionInfo.ErrorDiagnostic;

Data Types: char | string

Debug — Option to start programmatic simulation debugging session

"off" (default) | "on"

Option to start programmatic simulation debugging session, specified as "off" or "on".

This argument is supported only when you specify the first input to the sim function as a model name or handle.

Example: out = sim("MyModel",Debug="on");

Data Types: char | string

RapidAcceleratorUpToDateCheck — Option to disable rebuilding rapid accelerator target

"on" (default) | "off"

Option to disable rebuilding rapid accelerator target, specified as "on" or "off".

• "on" — Before each simulation, the software checks whether any changes to the model require rebuilding the rapid accelerator target. If a change requires rebuilding the rapid accelerator target, the software rebuilds the target before running the simulation.

• "off" — The software does not check whether changes to the model require rebuilding the rapid accelerator target and always runs the simulation without rebuilding the target. Changes to the model that require rebuilding the rapid accelerator target are ignored and are not reflected in the simulation.

This argument is supported only when you specify the first input to the sim function as a model name or handle.

Example: out = sim("MyModel",RapidAcceleratorUpToDateCheck="off");

Tips

To specify this option on a Simulink.SimulationInput object, use the setModelParameter function.

simin = Simulink.SimulationInput("MyModel");
simin = setModelParameter(simin,RapidAcceleratorUpToDateCheck="off");

Data Types: char | string

Timeout — Maximum simulation run time

positive scalar

Maximum simulation run time, specified as a positive scalar. Specify the time, in seconds, to allow the simulation to run. If the simulation runs for longer than the value you specify, the software issues a warning and stops the simulation. For example, if you specify Timeout as 30, the software stops the simulation and issues a warning if computing simulation results takes more than 30 seconds.

The Timeout parameter specifies a limit on the amount of clock time for a simulation to run. To specify the maximum time value to simulate, use the Stop time parameter.

This argument is supported only when you specify the first input to the sim function as a model name or handle.

Example: out = sim("MyModel",Timeout=60); runs a simulation with a 60-second timeout.

Tips

• Consider specifying a timeout when you use a variable-step solver. If simulation conditions constrain the step size, the solver starts taking very small time steps, which slows down the simulation.

• To specify this option on a Simulink.SimulationInput object, use the setModelParameter function.

  simin = Simulink.SimulationInput("MyModel");
  simin = setModelParameter(simin,Timeout=60);

Trace — Option to display summary of parameters before starting simulation

"siminfo"

Option to display summary of parameters before starting simulation, specified as "siminfo".

This argument is supported only when you specify the first input to the sim function as a model name or handle.

Example: out = sim("MyModel",Trace="siminfo");

Data Types: char | string

Output Arguments

out — Simulation results and metadata

Simulink.SimulationOutput object | array of Simulink.SimulationOutput objects | vector

Simulation results and metadata, returned as a Simulink.SimulationOutput object, an array of Simulink.SimulationOutput objects, or a vector. The Simulink.SimulationOutput object contains all data logged from simulation and metadata, such as timing information and diagnostics.

To ensure sim returns results in a consistent format for any syntax, save the model with the Single simulation output configuration parameter enabled.

The sim function returns a vector of the simulation time steps if all of these conditions are met:

• The only input argument is the name of the model.

• The Single simulation output parameter is disabled.

• Fast restart is disabled.

Tips

• To return results in the same format for every syntax, save the model with the Single simulation output parameter enabled. Returning all simulation data and metadata in a single object facilitates analyzing results from multiple simulations.

• To control execution and tune parameter values during scripted simulations, use the Simulation object. (since R2024a) For more information, see Run Simulations Programmatically.

• To interact with simulations using both the MATLAB Command Window and the Simulink Editor, issue simulation commands using the set_param function. For more information, see Run Simulations Programmatically.

• When you run a simulation using the sim function, the simulation runs until an error occurs or the simulation reaches the specified stop time.

• When you simulate a model with infinite stop time, stop the simulation from the MATLAB Command Window by pressing Ctrl+C. The simulation stops, and simulation results are not saved in the MATLAB workspace.

• Results of programmatic simulations are not available when the StopFcn model callback executes. To process simulation results, use the PostSimFcn callback of the Simulink.SimulationInput object instead.

• Configure logging for time, states, and outputs using the Configuration Parameters dialog box. On the Modeling tab, under Setup, click Model Settings. Then, in the Configuration Parameters dialog box, select Data Import/Export.

• To log signals throughout a model, use signal logging or logging blocks, such as the To Workspace block or the Record block. For more information, see Save Signal Data Using Signal Logging.

Version History

Introduced before R2006a

R2024a: View simulation time in Simulink Editor during simulation

When you run normal or accelerator mode simulations using the sim function and the model is open, the status bar at the bottom of the Simulink Editor window for the model updates to show the current simulation time during simulation.

R2024a: Consistent error handling for sim function with scalar Simulink.SimulationInput object

In prior releases, the sim function overwrote the CaptureErrors parameter for a single simulation if you specified one or more name-value arguments in addition to the scalar Simulink.SimulationInput object, including the StopOnError name-value argument. Now, the sim function has consistent default behavior and options, summarized in the table.

Simulink.SimulationInput Dimensions	CaptureErrors	StopOnError	Behavior Change
scalar	"off" by default. To enable this parameter, specify the parameter on the Simulink.SimulationInput object using the setModelParameter function.	This name-value argument has no effect when you run a single simulation.	Some calls to the sim function in scripts or functions from previous releases might not return a Simulink.SimulationOutput object when the same calls had returned the simulation output in previous releases. To restore the prior behavior, specify the CaptureErrors parameter as "on".
vector, matrix, array	Always "on".	"off" by default. Specify this name-value argument as "on" to skip subsequent simulations if a simulation error occurs.	No change.

R2024a: Run fast restart simulations using scalar Simulink.SimulationInput objects

You can configure a Simulink.SimulationInput object to enable fast restart for an individual simulation you run using the sim function and a scalar Simulink.SimulationInput object. Fast restart saves time in iterative simulation workflows by compiling the model only once, for the first simulation that has fast restart enabled. When you enable fast restart for an individual simulation using the sim function, at the end of the simulation, the FastRestart parameter remains enabled in the model and the model is initialized in fast restart.

The FastRestart parameter applies for only individual simulations you run one at a time. To use fast restart for multiple simulations you run together using an array of Simulink.SimulationInput objects, use the UseFastRestart name-value argument.

For more information, see How Fast Restart Improves Iterative Simulations.

R2024a: Code Analyzer warning for multiple output syntax

The Code Analyzer warns about calls to the sim function that return multiple output arguments. Since R2009b, the single simulation output syntaxes have been recommended, and the multiple output syntaxes have been discouraged.

Support for syntaxes that return multiple output arguments will be removed in a future release.

R2019a: Single simulation output parameter enabled by default for new models

The Single simulation output parameter is enabled by default for new models. When you simulate a model that has the Single simulation output parameter enabled, the simulation always returns simulation results as a single Simulink.SimulationOutput object.

Single simulation output syntaxes of the sim function have been recommended since R2009b. To ensure that the sim function always returns simulation results in a consistent format, save your models with the Single simulation output parameter enabled.

R2017a: Run individual or multiple simulations using Simulink.SimulationInput objects

The sim function has new syntaxes to support configuring simulations using one or more Simulink.SimulationInput objects. The Simulink.SimulationInput object represents a specification for the simulation that includes the initial state or operating point, external inputs, model parameter values, block parameter values, and variable values to use in the simulation. The values on the Simulink.SimulationInput object override values saved in the model for the simulation but do not modify or dirty the model.

The Simulink.SimulationInput object provides improved support and is recommended for parallel simulations along with the new parsim function.

R2009b: Easily analyze results from multiple simulations using single simulation output syntax

Using the new single-output syntaxes, you can return all simulation results and metadata as a single output argument. The single simulation output is a Simulink.SimulationOutput object that contains all data logged in the simulation as well as simulation metadata. Returning a single output argument provides better support for parallel simulations and facilitates analyzing results from multiple simulations.

To always return simulation results as a single output, save your model with the Single simulation output parameter enabled.

R2009b: Syntaxes that return multiple output arguments are not recommended

The sim function provides enhanced compatibility with parallel computing, including an option to simplify data and variable management by returning results as a single output. Syntaxes that return more than one output argument are not recommended.

To return results as a single output object, enable the Single simulation output configuration parameter in the model.

To simulate a model programmatically in R2009a and earlier, use this syntax.

[T,X,Y1,Y2,Yn] = sim('model',Timespan,Options,UT);

Only the model argument is required.

• If you do not specify other arguments, the simulation uses values in the model.

• If you specify additional arguments, those arguments override the values in the model.

• If you specify an argument as [], the simulation uses the value in the model.

The tables describe the input and output arguments and provide information about how to update your code to use syntaxes recommended for R2009b and later.

Input Argument Descriptions and Replacements

Input Argument	Argument Purpose and Value for R2009a and Earlier	Replacement
model	Name of model to simulate, specified as a character vector.	No change required. Starting in R2017a, you can specify the model to simulate using a Simulink.SimulationInput object that can also configure the model for simulation.
Timespan	Simulation start and stop times, specified as a scalar or a vector. TFinal — Specifies the stop time for the simulation, which starts from zero. [TStart TFinal] — Specifies the start time and the stop time for the simulation. [TStart OutputTimes TFinal] — Specifies start and stop times for the simulation along with output times for which to calculate a value. When you do not specify output times, the simulation engine determines the times for which to calculate values. Specifying output times ensures that the simulation computes a value for each time you specify.	Configure these options by specifying model configuration parameters as name-value arguments: Stop time — Specify the stop time for the simulation. Start time — Specify the start time for the simulation. Output times — Specify output times for which to calculate a value. Starting in R2017a, you can configure these options using a Simulink.SimulationInput object.
Options	One or more simulation parameters, specified as a structure.	Specify model configuration parameters using name-value arguments. Starting in R2017a, you can configure simulation options using a Simulink.SimulationInput object.
UT	External input data for root-level input ports.	Specify input data for root-level input ports using the Input parameter. Specify the parameter as a name-value argument. Starting in R2017a, you can specify external inputs using a Simulink.SimulationInput object.

Output Argument Descriptions and Replacements

Output Argument	Argument Purpose and Value for R2009a and Earlier	Replacement
T	Simulation times, returned as a vector.	Access time, states, and output data through the Simulink.SimulationOutput object. When you log time, states, and outputs, the SimulationOutput object contains the logged data, which you can access as a property using a dot and the variable name for the logged data. For example, if the SimulationOutput object is returned as the variable out, and you save time data to the variable tout: tout = out.tout; Use the model configuration parameters to specify data to log and the variables names for the logged data. Time States Output
X	Logged states, returned as an array or a structure.
Y1,Y2,...,YN	Logged outputs, returned as one or more vectors.

R2009b: SrcWorkspace argument not recommended

Starting in R2009b, the SrcWorkspace name-value argument is not recommended. Specifying this argument can lead to transparency violations for parallel simulations. Instead of using values defined in a workspace, specify values for simulation as inputs to the sim function.

• Before R2017a, specify parameter values for simulation using a structure that contains fields with names that match the parameter names and values that indicate the value to use for the parameter.

• Starting in R2017a, configure model parameter, block parameter, and variable values using a Simulink.SimulationInput object.