Create Simulation Data

First, create simulation data by simulating a model that logs data. This example uses the ex_sldemo_absbrake model and analyzes the effect of changing the Desired relative slip value.

Load the model. Use the set_param function to specify an initial value for the relative slip and simulate the model.

load_system('ex_sldemo_absbrake')

set_param('ex_sldemo_absbrake/Desired relative slip','Value','0.24')
out_1 = sim('ex_sldemo_absbrake');

Use the set_param function to specify a different value for the relative slip and simulate the model again.

set_param('ex_sldemo_absbrake/Desired relative slip','Value','0.25')
out_2 = sim('ex_sldemo_absbrake');

Compare Runs Using Global Tolerance Values

First, use the Simulink.sdi.getAllRunIDs function to get the run IDs that correspond to the last two simulation runs.

runIDs = Simulink.sdi.getAllRunIDs;
runID1 = runIDs(end - 1);
runID2 = runIDs(end);

Now, use the Simulink.sdi.compareRuns function to compare the runs. Specify a global relative tolerance value of 0.2 and a global time tolerance value of 0.5.

runResult = Simulink.sdi.compareRuns(runID1,runID2,'reltol',0.2,'timetol',0.5);

Check the Summary property of the returned Simulink.sdi.DiffRunResult object.

runResult.Summary

ans = struct with fields:
       OutOfTolerance: 2
      WithinTolerance: 2
            Unaligned: 0
        UnitsMismatch: 0
                Empty: 0
             Canceled: 0
          EmptySynced: 0
     DataTypeMismatch: 0
         TimeMismatch: 0
    StartStopMismatch: 0
          Unsupported: 0

Two signal comparisons within the run were within tolerance, and two were out of tolerance.

Plot Comparison Results

You can use plots to analyze the comparison results. Access the signal result for the Ww signal from the DiffRunResult object that contains the comparison results using the getResultByIndex function. Check the Status property of the Simulink.sdi.DiffSignalResult object.

signalResult_Ww = getResultByIndex(runResult,1)

signalResult_Ww = 
  DiffSignalResult with properties:

             Name: 'yout.Ww'
           Status: OutOfTolerance
          AlignBy: 'Path'
        SignalID1: 127816
        SignalID2: 127862
    MaxDifference: 12.4878
            Sync1: [1x1 timeseries]
            Sync2: [1x1 timeseries]
             Diff: [1x1 timeseries]

signalResult_Ww.Status

ans = 
OutOfTolerance

The Ww signal comparison results are out of tolerance. Plot the difference signal to analyze the result.

figure(1)
plot(signalResult_Ww.Diff)

Save Comparison Results

You can save the comparison results to an MLDATX file to analyze later or to share with a colleague. Use the saveResult function to save the run data and comparison results.

saveResult(runResult,'desiredSlipResults')

The MLDATX file desiredSlipResults is created in the working directory. Use the Simulink.sdi.load function or the open function to view the results in the MLDATX file.

Configure the Model

Load the model and mark signals of interest for logging. This example logs data for the q and alpha signals.

load_system('slexAircraftExample')

Simulink.sdi.markSignalForStreaming('slexAircraftExample/Aircraft Dynamics Model',3,'on')
Simulink.sdi.markSignalForStreaming('slexAircraftExample/Aircraft Dynamics Model',4,'on')

Run Simulations

Run simulations with different low-pass filter time constants to generate results to compare. The slexAircraftExample model stores variables associated with the model in the model workspace. To modify the time constant value, access the model workspace and use the assignin function.

out1 = sim('slexAircraftExample');

modelWorkspace = get_param('slexAircraftExample','modelworkspace');
assignin(modelWorkspace,'Ts',1)

out2 = sim('slexAircraftExample');

Access and Compare Simulation Results

Access the simulation results using the Simulation Data Inspector programmatic interface. Each simulation creates a run in the Simulation Data Inspector with a unique run ID. You use the run IDs to compare the simulation results.

runIDs = Simulink.sdi.getAllRunIDs;
runIDTs1 = runIDs(end-1);
runIDTs2 = runIDs(end);

Use the Simulink.sdi.compareRuns function to compare the data from the simulations. Then inspect the Status property of the signal result to see whether the signals fell within the default tolerance of 0.

diffRun1 = Simulink.sdi.compareRuns(runIDTs1,runIDTs2);

sig1Result1 = getResultByIndex(diffRun1,1);
sig2Result1 = getResultByIndex(diffRun1,2);

sig1Result1.Status

ans = 
OutOfTolerance

sig2Result1.Status

ans = 
OutOfTolerance

Compare Runs with Signal Tolerances

By default, signals use 0 for all tolerance values, so the comparison returns out-of-tolerance results when the signals are not identical. To further analyze the effect of the time constant change, specify tolerance values for the signals. You can specify tolerances for a programmatic comparison using the properties of the Simulink.sdi.Signal objects in the runs you compare. The comparison uses the tolerances specified for the baseline Signal object. This example specifies a combination of time and absolute tolerances.

To specify tolerances, first access the Simulink.sdi.Signal objects that correspond to each signal in the runs you want to compare.

run1 = Simulink.sdi.getRun(runIDTs1);
sigID1 = getSignalIDByIndex(run1,1);
sigID2 = getSignalIDByIndex(run1,2);

sig1 = Simulink.sdi.getSignal(sigID1);
sig2 = Simulink.sdi.getSignal(sigID2);

Check the Name property to identify each Signal object.

sig1.Name

ans = 
'q, rad/sec'

sig2.Name

ans = 
'alpha, rad'

Specify an absolute tolerance of 0.1 and a time tolerance of 0.6 for the q signal using the AbsTol and TimeTol properties of the q signal object in the baseline run.

sig1.AbsTol = 0.1;
sig1.TimeTol = 0.6;

Specify an absolute tolerance of 0.2 and a time tolerance of 0.8 for the alpha signal using the AbsTol and TimeTol properties of the alpha signal object in the baseline run.

sig2.AbsTol = 0.2;
sig2.TimeTol = 0.8;

Compare the runs again and access the results.

diffRun2 = Simulink.sdi.compareRuns(runIDTs1,runIDTs2);
sig1Result2 = getResultByIndex(diffRun2,1);
sig2Result2 = getResultByIndex(diffRun2,2);

Check the Status property of each signal to determine whether the comparison results fell within the specified tolerances.

sig1Result2.Status

ans = 
WithinTolerance

sig2Result2.Status

ans = 
WithinTolerance

Create Workspace Data

The Simulink.sdi.compareRuns function compares time series data. Create data for a sine wave to use as the baseline signal, using the timeseries format. Give the timeseries the name Wave Data.

time = 0:0.1:20;
sig1vals = sin(2*pi/5*time);
sig1_ts = timeseries(sig1vals,time);
sig1_ts.Name = 'Wave Data';

Create a second sine wave to compare against the baseline signal. Use a slightly different time vector and attenuate the signal so the two signals are not identical. Cast the signal data to the single data type. Also name this timeseries object Wave Data. The Simulation Data Inspector comparison algorithm will align these signals for comparison using the name.

time2 = 0:0.1:22;
sig2vals = single(0.98*sin(2*pi/5*time2));
sig2_ts = timeseries(sig2vals,time2);
sig2_ts.Name = 'Wave Data';

Create and Compare Runs in the Simulation Data Inspector

The Simulink.sdi.compareRuns function compares data contained in Simulink.sdi.Run objects. Use the Simulink.sdi.createRun function to create runs in the Simulation Data Inspector for the data. The Simulink.sdi.createRun function returns the run ID for each created run.

runID1 = Simulink.sdi.createRun('Baseline Run','vars',sig1_ts);
runID2 = Simulink.sdi.createRun('Compare to Run','vars',sig2_ts);

You can use the Simulink.sdi.compareRuns function to compare the runs. The comparison algorithm converts the signal data to the double data type and synchronizes the signal data before computing the difference signal.

basic_DRR = Simulink.sdi.compareRuns(runID1,runID2);

Check the Summary property of the returned Simulink.sdi.DiffRunResult object to see the result of the comparison.

basic_DRR.Summary

ans = struct with fields:
       OutOfTolerance: 1
      WithinTolerance: 0
            Unaligned: 0
        UnitsMismatch: 0
                Empty: 0
             Canceled: 0
          EmptySynced: 0
     DataTypeMismatch: 0
         TimeMismatch: 0
    StartStopMismatch: 0
          Unsupported: 0

The difference between the signals is out of tolerance.

Compare Runs and Check for Data Type Match

Depending on your system requirements, you may want the data types for signals you compare to match. You can use the Simulink.sdi.compareRuns function to configure the comparison algorithm to check for and report data type mismatches.

dataType_DRR = Simulink.sdi.compareRuns(runID1,runID2,'DataType','MustMatch');
dataType_DRR.Summary

ans = struct with fields:
       OutOfTolerance: 0
      WithinTolerance: 0
            Unaligned: 0
        UnitsMismatch: 0
                Empty: 0
             Canceled: 0
          EmptySynced: 0
     DataTypeMismatch: 1
         TimeMismatch: 0
    StartStopMismatch: 0
          Unsupported: 0

The result of the signal comparison is now DataTypeMismatch because the data for the baseline signal is double data type, while the data for the signal compared to the baseline is single data type.

Compare Runs and Check for Start and Stop Time Match

You can use the Simulink.sdi.compareRuns function to configure the comparison algorithm to check whether the aligned signals have the same start and stop times.

startStop_DRR = Simulink.sdi.compareRuns(runID1,runID2,'StartStop','MustMatch');
startStop_DRR.Summary

ans = struct with fields:
       OutOfTolerance: 0
      WithinTolerance: 0
            Unaligned: 0
        UnitsMismatch: 0
                Empty: 0
             Canceled: 0
          EmptySynced: 0
     DataTypeMismatch: 0
         TimeMismatch: 0
    StartStopMismatch: 1
          Unsupported: 0

The signal comparison result is now StartStopMismatch because the signals created in the workspace have different stop times.

Generate Simulation Data to Compare

Start by loading the slexAircraftExample system and marking signals of interest for logging.

load_system('slexAircraftExample')

Simulink.sdi.markSignalForStreaming('slexAircraftExample/Pilot',1,'on')
Simulink.sdi.markSignalForStreaming('slexAircraftExample/Aircraft Dynamics Model',... 
    4,'on')

This example runs two simulations of the slexAircraftExample model with different values for the variable Ts. Use get_param to access the model workspace for the slexAircraftExample model. Then, assign a value for the variable and run the first simulation.

modelWorkspace = get_param('slexAircraftExample','modelworkspace');
modelWorkspace.assignin('Ts',0.1);

out_1 = sim('slexAircraftExample');

Change the value of Ts and run the second simulation. Then,

modelWorkspace.assignin('Ts',0.2);

out_2 = sim('slexAircraftExample');
 

Use the Simulink.sdi.getAllRunIDs function to access the run IDs for the two simulation runs created when you simulated the slexAircraftExample model.

runIDs = Simulink.sdi.getAllRunIDs;
runID1 = runIDs(end-1);
runID2 = runIDs(end);

Define Alignment Criteria for the Comparison

Before running the comparison, define how you want the Simulation Data Inspector to align the signals between the runs. This example aligns signals by their name, then by their block path, and then by their Simulink identifier.

alignMethods = [Simulink.sdi.AlignType.SignalName
               Simulink.sdi.AlignType.BlockPath
               Simulink.sdi.AlignType.SID];

Compare the Runs with the Specified Alignment Criteria

Compare the simulation data in your two runs, using the alignment criteria you specified. The comparison uses a small time tolerance to account for the effect of differences in the step size used by the solver on the transition of the square wave input.

diffResults = Simulink.sdi.compareRuns(runID1,runID2,'align',alignMethods,...
    'timetol',0.005);

Check the Comparison Results for the Aligned Signals

You can use the getResultByIndex method to access the comparison results for the aligned signals in the runs you compared. You can use the Count property of the Simulink.sdi.DiffRunResult object to set up a for loop to check the Status property for each Simulink.sdi.DiffSignalResult object.

numComparisons = diffResults.count;

for k = 1:numComparisons
    resultAtIdx = getResultByIndex(diffResults,k);
    
    sigID1 = resultAtIdx.signalID1;
    sigID2 = resultAtIdx.signalID2;
    
    sig1 = Simulink.sdi.getSignal(sigID1);
    sig2 = Simulink.sdi.getSignal(sigID2);
    
    displayStr = 'Signals %s and %s: %s \n';
    fprintf(displayStr,sig1.Name,sig2.Name,resultAtIdx.Status);
end

Signals alpha, rad and alpha, rad: OutOfTolerance 
Signals Stick and Stick: WithinTolerance