Export Simulation Data

Exporting (logging) simulation data provides a baseline for analyzing and debugging a model. Use standard or custom MATLAB^® functions to generate simulated system input signals and to graph, analyze, or otherwise postprocess the system outputs.

Simulation Data

Simulation data can include any combination of signal, time, output, state, and data store logging data.

Exporting simulation data involves saving signal values to the MATLAB workspace or to a MAT-file during simulation for later retrieval and postprocessing. Exporting data is also known as “data logging” or “saving simulation data.”

You can have data logged in several formats:

• Simulink.SimulationData.Dataset

• Array

• Structure

• Structure with time

• MATLAB timeseries

• ModelDataLogs

  Note

  The ModelDataLogs class is supported for backward compatibility. Starting in R2016a, you cannot log data in the ModelDataLogs format. Signal logging uses Dataset format. In R2016a or later, when you open a model from an earlier release that had used ModelDataLogs format, the model will log data in Dataset format.

Consider converting data logged in other formats to Dataset format to simplify post-processing. For more information, see Dataset Conversion for Logged Data.

You can also use exported data as the input for simulating a model.

Approaches for Exporting Signal Data

Exporting simulation data often involves exporting signal data. You can use various approaches for exporting signal data.

Export Approach	Usage	Documentation
Connect a Scope block to a signal.	If you use a Scope block for viewing results during simulation, consider also using the Scope block to export data. Save output at a sample rate other than the base sample rate. Scopes store data and can be memory intensive.	Scope
Connect a signal to a To File block.	Consider using a To File block for exporting large amounts of data. Save output at a sample rate other than the base sample rate. Use the MAT-file only after the simulation has completed.	To File
Connect a signal to a To Workspace block.	Document in the diagram the workspace variables used to store signal data. Save output at a sample rate other than the base sample rate.	To Workspace
Connect a signal to a root-level Outport block.	Consider using this approach for logging data in a top-level model, if the model already includes an Outport block.	Outport
Set the signal logging properties for a signal.	Use signal logging to avoid adding blocks, such as Scope, To File, and To Workspace blocks, to your model. Log signals based on individual signal rates. Data is available when simulation is paused or completed. Use signal logging to log array of buses signals.	Export Signal Data Using Signal Logging
Configure Simulink® to export time, state, and output data.	To capture complete information about the simulation as a whole, consider exporting this data. Use the Output parameter to save root Outport block data during simulation. Outputs and states are logged at the base sample rate of the model.	Data Format for Logged Simulation Data Limit Amount of Exported Data Samples to Export for Variable-Step Solvers
Log a data store.	Log a data store to share data throughout a model hierarchy, capturing the order of all data store writes.	Log Data Stores
Use the sim command to log simulation data programmatically.	Use sim to export the time, states, and signal simulation data to one data object. Select the Return as single object parameter when simulating the model using the sim command inside a function or a parfor loop.	sim

Enable Simulation Data Export

To export the states and root-level output ports of a model to the MATLAB base workspace during simulation of the model, use one of these interfaces:

• Configuration Parameters > Data Import/Export pane (for details, see Model Configuration Parameters: Data Import/Export)

• sim command

In both approaches, specify:

• The kinds of simulation data that you want to export:

  • Signal logging

  • Time

  • Output

  • State or final state

  • Data store

  Each kind of simulation data export has an associated default variable. You can specify your own variables for the exported data.

• The characteristics of the logged data, including:

  • Data Format for Logged Simulation Data

  • Limit Data Logged

  • Samples to Export for Variable-Step Solvers

View Logged Data Using Simulation Data Inspector

To inspect exported simulation data interactively, consider using the Simulation Data Inspector.

The Simulation Data Inspector has some limitations on the kinds of logged data that it displays. See View Data with the Simulation Data Inspector.

Memory Performance

Optimization for Logged Data

When exporting simulation data in a simulation mode other than rapid accelerator, Simulink optimizes memory usage in the following situations.

• When time steps happen at regular intervals, Simulink uses compressed time representation. Simulink stores the value for the first timestamp, the length of the interval (time step), and the total number of timestamps.

• When multiple signals use identical timestamp sequences, the signals share a single stored timestamp sequence. Sharing a single stored timestamp can reduce memory use for logged data by as much as a factor of two. The difference in memory performance can be a critical performance factor, particularly when logging bus signals that have thousands of bus elements.

Logging to Persistent Storage

You can encounter memory issues when you log many signals in a long simulation that has many time steps. Logging to persistent storage can address this kind of memory issue.

To log to persistent storage, in the Configuration Parameters > Data Import/Export pane, select Log Dataset data to file option. Specify the kinds of logging (for example, signal logging and states logging).

• For logging output and states data, set the Format parameter to Dataset.

• If you select the Final states parameter, clear the Save final operating point parameter.

Using a Simulink.SimulationData.DatasetRef object to access signal logging and states logging data loads data into the model workspace incrementally. Accessing data for other kinds of logging loads all the data at once.

For details, see Log Data to Persistent Storage.