Log data to file

Option to log data that uses Dataset format to MAT or MLDATX file

Model Configuration Pane: Data Import/Export

Description

The Log data to file parameter specifies whether simulation data that uses the Dataset format is logged to a MAT or MLDATX file or logged to the workspace.

Log data to a MAT or MLDATX file by specifying the file extension as .mat or .mldatx. For example, to log data to an MLDATX file named myData, type myData.mldatx.

Logging data to an MLDATX file typically results in a smaller file size. The MLDATX file created when you select Log data to file is similar to a Simulation Data Inspector session file, but it contains only the data for a single run without view or comparison information.

This table shows the type of data that can be logged to each file type.

Logged Data	File Type
	MAT file	MLDATX file
Output saved in Dataset format	Yes	Yes
Signal logging data	Yes	Yes
States saved in Dataset format	Yes	Yes
Final states saved in Dataset format	Yes	No
Data stores	Yes	Yes
Data logged using a Record block	No	Yes
Data logged using a To Workspace block	No	Yes
Data logged using a Scope block configured to log data to the workspace	No	Yes

To log states or output data to a file, set the Save format parameter to Dataset.

To log Final states data to a MAT file, set the Save format parameter to Dataset and clear Save final operating point. MLDATX files do not support logging Final states data.

Tip

To log operating point data to a MAT file, log the model operating point during simulation. For more information, see Speed Up Simulation Workflows by Using Model Operating Points.

Settings

off (default) | on

off

Simulation data logged using the Dataset format logs to the workspace and does not log to a file.

on

Simulation data logged using Dataset format logs to a MAT or MLDATX file and does not log to the workspace. By default, data is saved in a MAT file with the name out.mat in the current working directory. To log data to an MLDATX file, change the file extension to .mldatx. To save the file in a different location or using a different filename, specify the path and filename in the text box.

Tips

• When the data in the MAT file fits into memory, use the load function to access the data.

• To access the data in an MLDATX file, use the Simulink.sdi.load to load the data. Then, use the Simulink.sdi.Run.getLatest function to get the Simulink.sdi.Run object associated with the loaded MLDATX file. To export the data to the workspace, use the export function.

  Simulink.sdi.load("out.mldatx")
  runObj = Simulink.sdi.Run.getLatest;
  dataset = export(runObj);

• When the data in the MAT file is too large to fit into memory, access the data in the MAT file using Simulink.SimulationData.DatasetRef and matlab.io.datastore.SimulationDatastore objects.

• Except for parallel simulations, the software overwrites the contents of the file during each simulation unless you change the name of the file between simulations. For details, see Save Logged Data from Successive Simulations.

Note

To log data to an MLDATX file, in Preferences > Storage, check that the default setting of View and record data is selected. If you select View during simulation only instead, the MLDATX file contains the logged signal name, but does not include the data.

Recommended Settings

The table summarizes recommended values for this parameter based on considerations related to code generation.

Application	Setting
Debugging	No impact
Traceability	No impact
Efficiency	No recommendation
Safety precaution	No recommendation

Programmatic Use

Parameter: LoggingToFile

Value: "on" | "off"

Default: 'off'

Parameter: LoggingFileName

Type: string | character vector

Value: valid path and file name

Default: 'out.mat'

Version History

Introduced in R2016a

R2025a: Log data to MLDATX file

You can log data to an MLDATX file by specifying the file extension as .mldatx.

R2025a: Log data to file in simulations run using Simulation objects

The Simulation object supports logging data that uses Dataset format to a file in normal mode simulations.

To enable the parameter on the Simulation object, use the setModelParameter function.

sm = setModelParameter(sm,LoggingToFile="on");