Setup

This example continues from Inspect Simulation Data. You can also use this script to generate the data required for the example.

load_system('slexAircraftExample')

% Configure signals to log
Simulink.sdi.markSignalForStreaming('slexAircraftExample/Pilot', 1, 'on')
Simulink.sdi.markSignalForStreaming('slexAircraftExample/Aircraft Dynamics Model', 3, 'on')
Simulink.sdi.markSignalForStreaming('slexAircraftExample/Aircraft Dynamics Model', 4, 'on')

% Change Pilot signal to sine
set_param('slexAircraftExample/Pilot', 'WaveForm', 'sine')

% Simulate model
sim('slexAircraftExample')

ans = 
  Simulink.SimulationOutput:
                logsout: [1x1 Simulink.SimulationData.Dataset] 
                   tout: [1235x1 double] 
                   xout: [1x1 Simulink.SimulationData.Dataset] 
                   yout: [1x1 Simulink.SimulationData.Dataset] 

     SimulationMetadata: [1x1 Simulink.SimulationMetadata] 
           ErrorMessage: [0x0 char] 

% Change Pilot signal to square
set_param('slexAircraftExample/Pilot', 'WaveForm', 'square')

% Simulate Model
sim('slexAircraftExample')

ans = 
  Simulink.SimulationOutput:
                logsout: [1x1 Simulink.SimulationData.Dataset] 
                   tout: [1381x1 double] 
                   xout: [1x1 Simulink.SimulationData.Dataset] 
                   yout: [1x1 Simulink.SimulationData.Dataset] 

     SimulationMetadata: [1x1 Simulink.SimulationMetadata] 
           ErrorMessage: [0x0 char] 

Compare Signals

You can compare signals to analyze the relationship between two signals in a model. For example, compare the Stick input signal to the output signal, alpha, rad.

Alternatively, you can select the Baseline and Compare to signals using the context menu by right-clicking the signal in the Inspect pane.

The signals are not identical, so they do not match within the absolute, relative, and time tolerances, all set to 0 by default.

Compare Runs

You can also use the Simulation Data Inspector to compare all the signals in a run to all the signals in another run. Run comparisons can provide useful information about the effects of changing model parameters. For example, change the frequency cutoff of the filter for the control stick input signal. Then, evaluate the effect on the logged signals using the Simulation Data Inspector.

The Compare pane lists all signals from the compared runs and summarizes the results of the comparison in the Results column. In this example, all three signals aligned, and none matched. You can click More to see the reason each signal comparison did not match. All three signals are out of tolerance.

To plot a comparison result, select the signal you want to view in the Compare pane. For example, select the result for the q, rad/sec signal. The top plot shows the q, rad/sec signals from the Baseline and Compare To runs. The bottom plot shows the difference between the signals and the calculated tolerance band.

Configure Comparison Constraints

You can also apply constraints to comparisons that affect whether the result is a match or mismatch. For example, you can specify that the time vectors for signals must match in order for the result to be a match. To specify the constraint, click More, then select Signal time vectors must match. To run a new comparison with this constraint, click Compare.

The comparison results show all signal results as mismatches now. The time vectors do not match for any of the signals because they were logged from simulations of a model that uses a variable-step solver, and the conditions changed between simulations. When the comparison result is a mismatch due to a constraint, the Simulation Data Inspector does not compute results for that signal. When you select a signal, the plot area shows an explanation of why the signal result is a mismatch.

You can configure these comparison constraints:

When you require a match in signal metadata, specifying a constraint can return a mismatch result more quickly because the comparison does not compute results when the specified metadata does not match.

You can also configure a comparison to stop computing results after detecting the first mismatch result. When you configure a comparison to stop on the first mismatch, the comparison always stops after detecting the first mismatch in the signal metadata. You can also choose to stop the comparison when the first mismatch result is due to an out-of-tolerance result when comparing the signal data.

The Simulation Data Inspector always aligns signals in the baseline and comparison runs and always checks whether signal units match. When you configure a comparison to stop on the first mismatch, signals that do not align and signals with units that do not match always cause a comparison to stop. You can specify additional metadata for the comparison to check by selecting one or more constraints.

Cancel Comparisons

The runs and signals used in this example are relatively small, and comparisons run quickly. When you compare long signals or runs containing many signals, comparisons may take more time. The Simulation Data Inspector displays incremental progress indicators during comparison, and the Compare button becomes a Cancel button you can click to cancel the comparison at any point. For hierarchical data, the Results column in the comparison view summarizes the results on each hierarchical node.