Investigate Signal Values

While transmitting valuable data about a model and between the blocks, signals may take different values. In this section, you learn how to initialize, display signals as well as more information on the data types and dimensions a signal can take.

Initialize Signal Values

If a signal does not have an explicit initial value, the initial value that Simulink^® uses depends on the data type of the signal.

Signal Data Type	Default Initial Value
Numeric (other than fixed-point)	Zero
Fixed-point	Real-world ground value
Boolean	False
Enumerated	Default value

You can specify the non-default initial values of signals for Simulink to use at the beginning of simulation.

For any signal, you can define a signal object (Simulink.Signal), and use that signal object to specify an initial value for the signal.
For some blocks, such as Outport, Data Store Memory, and Memory, you can use either a signal object or a block parameter, or both, to specify the initial value of a block state or output.

For details, see Initialize Signals and Discrete States.

View Signal Values

You can use either blocks or the signal viewers (such as the Signal & Scope Manager) to display the values of signals during a simulation. For example, you can use either the Scope block or the Signal & Scope Manager to graph time-varying signals on an oscilloscope-like display during simulation. For general information about options for viewing signal values, see Scope Blocks and Scope Viewer Overview. For detailed information about:

Blocks that you can use to display signals in a model, see Sinks
Signal viewers, Floating Scope and Scope Viewer Tasks
The Signal & Scope Manager, see Viewers and Generators Manager
Test points, which are signals that Simulink guarantees to be observable when using a Floating Scope block in a model, see Configure Signals as Test Points.

Display Signal Values in Model Diagrams

To include graphical displays of signal values in a model diagram, use one of the following approaches:

Display Data Tips During Simulation

For many blocks, Simulink can display block output (port values) as data tips on the block diagram while a simulation is running.

In the Simulink Editor, on the Debug tab, select Output Values , go to the Signal tab, and toggle on the Output Value Label > Toggle Value Displays button.
To change display options, use the Options submenu.

For details, see View Signal Values Using Port Value Labels.

Display Signal Value After Simulation

To display, below a specific signal, the signal value after simulation:

Right-click the signal.
In the context menu, select Show Value Label of Selected Port.

Signal Data Types

Data type refers to the format used to represent signal values internally. By default, the data type of Simulink signals is double. You can create signals of other data types. Simulink signals support the same range of data types as MATLAB^®. See About Data Types in Simulink for more information.

Complex Signals

The values of signals can be complex numbers or real numbers. A signal whose values are complex numbers is a complex signal. Create a complex-valued signal using one of the following approaches:

Load complex-valued signal data from the MATLAB workspace into the model via a root-level Inport block.
Create a Constant block in your model and set its value to a complex number.
Create real signals corresponding to the real and imaginary parts of a complex signal, then combine the parts into a complex signal, using the Real-Imag to Complex conversion block.

Manipulate complex signals via blocks that accept them. If you are not sure whether a block accepts complex signals, see the documentation for the block.

Exporting Signal Data

You can save signal values to the MATLAB workspace during simulation, for later retrieval and postprocessing. For a summary of different approaches, see Save Simulation Data.