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State Information

Simulation State Information

Some blocks maintain state information that they use during simulation. For example, the state information for a Unit Delay block is the output signal value from the previous simulation step. The block uses the state information to calculate the output value for the current simulation step.

Some examples of how saved state information is used include:

  • Stopping a simulation for a model and using the saved state information as input when you restart the simulation.

  • Simulating one model and using the saved state information as input for the simulation of another model that builds on the results of the first model.

  • Examining changes in state information throughout a simulation.

Types of State Information

You can save these kinds of state information.

Type of State InformationDescriptionConfiguration Parameters in Data Import/Export Pane
States for each simulation stepState information of blocks (referred to as partial state data) at each time step of a simulationStates
Final stateState information of blocks at the end of the simulationFinal states
Final state with ModelOperatingPointFinal state with a ModelOperatingPoint object that captures additional internal information that Simulink® uses during simulationFinal States and Save final operating point

ModelOperatingPoint provides more complete final simulation state information than final states information by itself does. However, if the requirements and limitations of using ModelOperatingPoint do not meet your modeling requirements, save final state information without ModelOperatingPoint.

Comparison of Operating Point and Final State Logging

CharacteristicFinal StateFinal State with Operating Point

Simulation mode

Supports all simulation modes

Supports all simulation modes

Model reference

State Information for Referenced Models

See Model Referencing.

Resumed simulation

Not supported


Saved state data

Only logged states — the continuous and discrete states of blocks — which are a subset of the complete simulation state of the model

User data, run-time parameters, or logs of the model not saved

Complete state information.

Does not save user data, run-time parameters, or logs of the model.

Block output

User data, run-time parameters, or logs of the model not saved

Simulink tries to save the output of a block as part of a ModelOperatingPoint object even if S-functions declare that no ModelOperatingPoint objects exist in the block. If the block output is of custom type, Simulink displays an error.


Use structure with time format for best readability

To examine a simplified view of the data, consider using the loggedStates property of the Simulink.op.ModelOperatingPoint class.

Restoring state data

Can save and restore in different simulation modes. If logged state information is not sufficient, you can obtain different results in the normal mode and the accelerator mode.

Cannot save in normal mode and restore in accelerator mode, or conversely save in accelerator mode and restore in normal mode.

Restoring multiple states

You can initialize only one out of multiple logged states in the model.

You restore all states in the model. You cannot load a subset of states.

Structural changes

You can make structural changes between simulation and restoring the simulation.

You cannot make structural changes to the model between when you save the ModelOperatingPoint object and when you restore the simulation using the ModelOperatingPoint object. For example, you cannot add or remove a block after saving the ModelOperatingPoint object without repeating the simulation and saving the new ModelOperatingPoint object.

Input to model function

To input to model function, use Array format with non-complex data of type double.

You cannot input the ModelOperatingPoint object to model function.

Code generation


Not supported.

For both ModelOperatingPoint and final state logging, Simulink saves state information at one of these points:

  • At the final time step

  • At the execution time at which the simulation paused or stopped

For additional information about ModelOperatingPoint, see Limitations of Saving and Restoring Operating Point.

Format for State Information Saved Without Operating Point

If you do not use the ModelOperatingPoint for saving state information, then use Configuration Parameters > Data Import/Export > Format to specify the data format for the saved state information.

You can set Format to:

  • Dataset (default)

  • Array

  • Structure

  • Structure with time

The default setting for the Format parameter is Dataset. The Dataset format:

  • Stores logged data in timeseries or timetable objects. You can work with data saved in a timeseries or timetable object in MATLAB® without a Simulink license.

  • Supports logging multiple data values for a given time step, which can be required for logging data in a For Iterator Subsystem, a While Iterator Subsystem, and Stateflow®.

  • Does not support logging states inside a function-call subsystem or during rapid accelerator simulations.

  • Does not support code generation.

Signal logging always uses the Dataset format. Logging states data using the Dataset format allows you to post-process simulation data without writing custom code for different types of logged data. When you log states using the Dataset format, the data also automatically streams to the Simulation Data Inspector during simulation.

The Array option for the Format parameter exists for backward compatibility with models developed in earlier releases, when Simulink supported only the Array format for logging state information. The order of signals within the array depends on the block sorted order, which can change from one simulation to another when you change any of the following:

  • The model (even without changing the signal)

  • The simulation mode

  • The code generation mode

The variation in signal order can present challenges when post-processing the logged data.

The Structure and Structure with time formats are useful when using state information to initialize a model for simulation, allowing you to:

  • Associate initial state values directly with the full path name to the states. This association eliminates errors that can occur if Simulink reorders the states, but the order of the initial state array does not change correspondingly.

  • Assign a different data type to the initial value of each state.

  • Initialize only a subset of the states.

State Information for Referenced Models

When Simulink saves states in the structure or structure-with-time format, it adds an inReferencedModel subfield to the signals field of the structure. The value of this additional subfield is true (1) if the signals field records the final state of a block that resides in the referenced model. For example:

ans = 

               values: [101x1 double]
           dimensions: 1
                label: 'DSTATE'
            blockName: [1x66 char]
    inReferencedModel: 1

If the signals field records a referenced model state, its blockName subfield contains a compound path of a top model path and a referenced model path. The top model path is the path from the model root to the Model block that references the referenced model. The referenced model path is the path from the referenced model root to the block whose state the signals field records. The compound path uses a | character to separate the top and referenced model paths. For example:

>> xout.signals(1).blockName
ans =

sldemo_mdlref_basic/CounterA|sldemo_mdlref_counter/Previous Output

See Also


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