simscape.logging.export

Save logged simulation data in MLDATX file

Syntax

simscape.logging.export(simlog,fileName)

Description

simscape.logging.export(simlog,fileName) saves the simlog object, containing logged simulation data, for future use. You can use this function only for data logged with the Stream data to temporary disk directory preference turned on.

When you stream simulation data to disk, the data is stored as a simlog object in a temporary file, and the workspace logging variable references the simlog object. The temporary file persists as long as there is a logging variable in the workspace that references the file. This function lets you save the simlog object to a different file, specified by the fileName argument, in MLDATX format.

Examples

Save Logged Simulation Data Streamed to Disk

To enable streaming data to disk, on the MATLAB^® Toolstrip, click Preferences. In the left pane of the Preferences dialog box, select Simscape, then select the Stream data to temporary disk directory check box.

Open the Permanent Magnet DC Motor example model, which already has data logging enabled, and run the simulation:

openExample('simscape/PermanentMagnetDCMotorExample')
sim('PermanentMagnetDCMotor');

During the simulation, logged data is streamed to disk, to a temporary MLDATX file. After the simulation, you see the simulation log variable simlog_PermanentMagnetDCMotor (as specified by the Workspace variable name model configuration parameter) in your current workspace:

simlog_PermanentMagnetDCMotor

simlog_PermanentMagnetDCMotor = 

  Node with properties:

              id: 'PermanentMagnetDCMotor'
         savable: 0
      exportable: 1
        DC_Motor: [1×1 simscape.logging.Node]
     MRRef_Motor: [1×1 simscape.logging.Node]
            ERef: [1×1 simscape.logging.Node]
     Load_Torque: [1×1 simscape.logging.Node]
      Step_Input: [1×1 simscape.logging.Node]
      DC_Voltage: [1×1 simscape.logging.Node]
    MRRef_Torque: [1×1 simscape.logging.Node]
         Sensing: [1×1 simscape.logging.Node]

The exportable: 1 property of the simlog_PermanentMagnetDCMotor variable indicates that this variable points to the temporary file on disk, which contains the simulation data. The temporary file exists as long as the variable exists in your workspace, then it is deleted.

To save the logged simulation data for future use, type:

simscape.logging.export(simlog_PermanentMagnetDCMotor,'C:\Work\motor_run1');

This command creates a file under C:\Work, named motor_run1.mldatx, and stores the logged simulation data in this file, in MLDATX format.

To retrieve the logged simulation data at a later time and associate it with a workspace variable, use the simscape.logging.import function.

Input Arguments

simlog — Logged simulation data

Node object

Logged simulation data, specified as a Node object, with the exportable property set to 1. You refer to the simlog object by the name of the corresponding simulation log workspace variable. You specify the name of the simulation log variable by using the Workspace variable name parameter in the Simscape pane of the Configuration Parameters dialog box.

fileName — File name and path

character vector | string scalar

File name and path, specified as a character vector or string scalar. The function stores the simlog object in the specified file, in MLDATX or HDF5 format. If you omit the file extension, the data is stored in an MLDATX file. To save the simlog object in HDF5 format, the fileName character vector must include the .h5 extension. If you specify a file extension other that .h5 or .mldatx, you get an error. If you do not include the path, the file resides in the current working directory.

If the file already exists, the function overwrites it without a warning. However, if you import a node from a file, and then try to export it to the same file, a message informs you that in this case the file cannot be overwritten.

Example: 'C:\Work\motor_run1.mldatx'

Data Types: char | string

Version History

Introduced in R2016a

R2020b: File format when streaming logged simulation data to disk has changed from HDF5 to MLDATX

In R2020b, the file format for streaming logged simulation data to disk has changed from HDF5 to MLDATX. As a result, the default format for simscape.logging.export and simscape.logging.import has also changed to MLDATX. However, you can still export and import HDF5 files:

• When you use simscape.logging.export without specifying the file extension, the data is stored in an MLDATX file in the temporary directory.

• Currently, you can still export data in HDF5 format, to share it with colleagues who are using older software releases. To do this, specify .h5 file extension when using simscape.logging.export. The function stores the data in HDF5 format and issues a warning that this functionality will be removed in a future release. If you specify a file extension other that .h5 or .mldatx, you get an error.

• When you import an HDF5 file from a previous release using simscape.logging.import, the data is automatically converted to the new format, loaded into the Node object, and copied to a binary MLDATX file in the temporary directory. If there are two files with the same name and different extensions (.h5 and .mldatx), then the MLDATX file is loaded.