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Data Format for Logged Simulation Data

Data Format for Block-Based Logged Data

You can use the Scope, To File, or To Workspace blocks to export simulation data. Each of these blocks has a data format parameter.

Data Format for Model-Based Logged Data

The data format for model-based exporting of simulation data specifies how Simulink® stores the exported data.

Simulink uses different data formats, depending on the kind of data that you export. For details, see:

Logged Data Store Format

When you log data store data, Simulink uses a Simulink.SimulationData.Dataset object.

For details, see Accessing Data Store Logging Data.

Time, State, and Output Data Format

For exported time, states, and output data, use one of the following formats:

If you select the Configuration Parameters > Data Import/Export > Output check box, Simulink logs fixed-point data as double. To log fixed-point data, consider using one of these approaches:

  • Signal logging — For details, see Export Signal Data Using Signal Logging.

    1. In the Simulink Editor, select one or more signals.

    2. Click the Simulation Data Inspector button arrow and click Log Selected Signals to Workspace.

  • To File block

  • To Workspace block — In the To Workspace Block Parameters dialog box, enable the Log fixed-point data as a fi object parameter.

For information about the format for logged final state data, see State Information.

Dataset

Dataset format:

  • Uses MATLAB® timeseries objects to store logged data. MATLAB timeseries objects allow you to work with logged data in MATLAB without a Simulink license.

  • Supports logging multiple data values for a given time step, which can be important for Iterator subsystem and Stateflow® signal logging.

  • Supports inclusion of units information in logged data for output data

  • Does not support logging nonvirtual bus data for code generation or in rapid accelerator mode.

Array

If you select this Array option, Simulink saves the states and outputs of a model in a state and output array, respectively.

The state matrix has the name specified in the Configuration Parameters > Data Import/Export pane (for example, xout). Each row of the state matrix corresponds to a time sample of the states of a model. Each column corresponds to an element of a state. For example, suppose that your model has two continuous states, each of which is a two-element vector. Then the first two elements of each row of the state matrix contain a time sample of the first state vector. The last two elements of each row contain a time sample of the second state vector.

The model output matrix has the name specified in the Configuration Parameters > Data Import/Export pane (for example, yout). Each column corresponds to a model output port, and each row to the outputs at a specific time.

    Note:   Use array format to save your model outputs and states only if the logged data meets all these conditions:

    • Data is all scalars or all vectors (or all matrices for states)

    • Data is all real or all complex

    • Data all has the same data type

    If your model outputs and states do not meet these conditions, use the Structure or Structure with time output formats (see Structure with Time).

Structure with Time

If you select this format, Simulink saves the model states and outputs in structures that have their names specified in the Configuration Parameters > Data Import/Export pane. By default, the structures are xout for states and yout for output.

The structure used to save outputs has two top-level fields:

  • time

    Contains a vector of the simulation times.

  • signals

    Contains an array of substructures, each of which corresponds to a model output port.

Each substructure has four fields:

  • values

    Contains the outputs for the corresponding output port.

    • If outputs are scalars or vectors — values field is a matrix each of whose rows represent an output at the time specified by the corresponding time vector element.

    • If the outputs are matrix (2-D) values — values field is a 3-D array of dimensions M-by-N-by-T. M-by-N is the dimensions of the output signal and T is the number of output samples.

    • If T = 1 — MATLAB drops the last dimension. Therefore, the values field is an M-by-N matrix.

  • dimensions

    Specifies the dimensions of the output signal.

  • label

    Specifies the label of the signal connected to the output port, S-Function block, or the type of state (continuous or discrete). The label is DSTATE or CSTATE, except for S-Function block state labels. For S-Function block state labels for discrete states, the label is the name of the state (instead of DSTATE).

  • blockName

    Specifies the name of the corresponding output port or block with states.

  • inReferencedModel

    If the signals field records the final state of a block that resides in the reference model, contains a value of 1. Otherwise, the value is false (0).

The following example shows the structure-with-time format for a nonreferenced model.

xout.signals(1) 
ans = 

               values: [296206x1 double]
           dimensions: 1
                label: 'CSTATE'
            blockName: 'vdp/x1'
    inReferencedModel: 0

The structure used to save states has a similar organization. The states structure has two top-level fields:

  • time

    The time field contains a vector of the simulation times.

  • signals

    The field contains an array of substructures, each of which corresponds to one of the states of the model.

Each signals structure has four fields: values, dimensions, label, and blockName. The values field contains time samples of a state of the block specified by the blockName field. The label field for built-in blocks indicates the type of state: either CSTATE (continuous state) or DSTATE (discrete state). For S-Function blocks, the label contains whatever name is assigned to the state by the S-Function block.

The time samples of a state are stored in the values field as a matrix of values. Each row corresponds to a time sample. Each element of a row corresponds to an element of the state. If the state is a matrix, the matrix is stored in the values array in column-major order. For example, suppose that the model includes a 2-by-2 matrix state and that 51 samples of the state are logged during a simulation run.

The values field for this state would contain a 51-by-4 matrix. Each row corresponds to a time sample of the state, and the first two elements of each row correspond to the first column of the sample. The last two elements correspond to the second column of the sample.

Structure

This format is the same as for Structure with time output format, except that Simulink does not store simulation times in the time field of the saved structure.

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