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Adding a Transient Parameter to ATLAS#

This guide demonstrates how to add a transient parameter to an ATLAS session, retrieve data from an existing parameter, perform a transformation, and write the result to the new transient parameter.

Overview:

  1. Create a transient parameter.
  2. Retrieve the time base and source parameter (vCar).
  3. Estimate the number of samples.
  4. Read the data and apply a transformation (vCar * 2).
  5. Write the transformed data to the transient parameter.

Parameters

  • DemoDisplayName: "Demo Waveform"
  • ParameterName: "vCar:Chassis"
  • TransientParameterName: "vCar2 Demo"
  • Range: 0 to 800

Define Transient Parameter Metadata#

This section sets up the necessary metadata for the transient parameter. It includes the display name, identifier, description, value range, and grouping information. These values are used to register the parameter in the ATLAS session and define how it will appear and behave.

    string demoDisplayName = "Demo Waveform";
    string parameterName = "vCar:Chassis";
    string transientParameterDescription = "vCar2 Demo";
    string transientParameterGroups = "";
    string transientParameterIdentifier = "vCar2 Demo";
    double transientParameterMaximum = 800;
    double transientParameterMinimum = 0;
    string transientParameterName = "vCar2 Demo";

    DemoDisplayName = "Demo Waveform"
    ParameterName = "vCar:Chassis"
    TransientParameterDescription = "vCar2 Demo"
    TransientParameterGroups = ""
    TransientParameterIdentifier = "vCar2 Demo"
    TransientParameterMaximum = 800
    TransientParameterMinimum = 0
    TransientParameterName = "vCar2 Demo"

    demoDisplayName = 'Demo Waveform';
    parameterName = 'vCar:Chassis';
    transientParameterDescription = 'vCar2 Demo';
    transientParameterGroups = '';
    transientParameterIdentifier = 'vCar2 Demo';
    transientParameterMaximum = 800;
    transientParameterMinimum = 0;
    transientParameterName = 'vCar2 Demo';

Create Transient Parameter#

The transient parameter is created and registered within the current ATLAS session. A transient parameter is temporary and used to store calculated or transformed data during the session. This step ensures the system is ready to receive new data.

    var transientParameter = sessionServiceClient.AddTransientParameter(
    sessionId,
    transientParameterIdentifier,
    demoDisplayName,
    transientParameterDescription,
    transientParameterGroups.Split(';'),
    transientParameterMinimum,
    transientParameterMaximum
);

    transient_parameter = sessionServiceClient.AddTransientParameter(
    sessionId,
    TransientParameterIdentifier,
    DemoDisplayName,
    TransientParameterDescription,
    TransientParameterGroups.split(";"),
    TransientParameterMinimum,
    TransientParameterMaximum
)

    transientParameter = sessionServiceClient.AddTransientParameter( ...
    sessionId, ...
    transientParameterIdentifier, ...
    demoDisplayName, ...
    transientParameterDescription, ...
    strsplit(transientParameterGroups, ';'), ...
    transientParameterMinimum, ...
    transientParameterMaximum);

Tip

A transient parameter is temporary—it exists only while the session is active in ATLAS.

Once the session is closed or disposed, the transient parameter and its data are permanently lost.

✅ Use transient parameters for:

  • Intermediate calculations
  • Temporary visualizations
  • Session-specific data transformations

❌ Do not use them for storing data that needs to persist beyond the session.

Retrieve Time Base and Source Parameter#

This step retrieves two critical pieces of information:

The time base, which defines the start and end times for the session data. The source parameter (vCar), which contains the original data that will be transformed. These are needed to align the new data with the existing session timeline and to access the correct input values.

    var timebase = sessionServiceClient.GetSessionTimeBase(sessionId);
    var parameter = sessionServiceClient.GetSessionParameter(sessionId, "vCar");

    timebase = sessionServiceClient.GetSessionTimeBase(sessionId)
    parameter = sessionServiceClient.GetSessionParameter(sessionId, 'vCar')

    timebase = sessionServiceClient.GetSessionTimeBase(sessionId);
    parameter = sessionServiceClient.GetSessionParameter(sessionId, 'vCar');

Estimate Sample Count and Navigate to Start#

Before reading data, we estimate how many samples exist for the selected parameter within the time base. This helps optimize memory and performance. We also move the internal cursor to the start of the time base to ensure data is read from the beginning.

    int sampleCount = parameterDataAccessServiceClient.GetSamplesCountEstimate(
    sessionId,
    parameter.Identifier,
    timebase.StartTime,
    timebase.EndTime
    );

    parameterDataAccessServiceClient.Goto(sessionId, parameter.Identifier, timebase.StartTime);

    sample_count = parameterDataAccessServiceClient.GetSamplesCountEstimate(
    sessionId,
    parameter.Identifier,
    timebase.StartTime,
    timebase.EndTime
    )

    parameterDataAccessServiceClient.Goto(sessionId, parameter.Identifier, timebase.StartTime)

    sampleCount = parameterDataAccessServiceClient.GetSamplesCountEstimate( ...
    sessionId, ...
    parameter.Identifier, ...
    timebase.StartTime, ...
    timebase.EndTime);

    parameterDataAccessServiceClient.Goto(sessionId, parameter.Identifier, timebase.StartTime);

Retrieve and Transform Data#

In this step, the original data samples are retrieved from the source parameter. Each sample is checked for validity, and a transformation is applied—in this case, multiplying each value by 2. The transformed values and their corresponding timestamps are stored for later use.

    var timestamps2 = new List<DateTime>();
    var values2 = new List<double>();

    var values = parameterDataAccessServiceClient.GetNextSamples(sessionId, parameter.Identifier, sampleCount);

    for (int i = 0; i < values.Data.Length; i++)
    {
        if (values.DataStatus[i] == DataStatusType.Sample)
        {
            timestamps2.Add(values.Time[i]);
            values2.Add(values.Data[i] * 2);
        }
    }

    timestamps2 = []
    values2 = []

    values = parameterDataAccessServiceClient.GetNextSamples(sessionId, parameter.Identifier, sample_count)

    for status, data, time in zip(values.DataStatus, values.Data, values.Time):
        if status == DataStatusType.Sample:
            timestamps2.append(time)
            values2.append(data * 2)

    timestamps2 = [];
    values2 = [];

    values = parameterDataAccessServiceClient.GetNextSamples(sessionId, parameter.Identifier, sampleCount);

    for i = 1:length(values.Data)
        if values.DataStatus(i) == DataStatusType.Sample
            timestamps2(end+1) = values.Time(i);
            values2(end+1) = values.Data(i) * 2;
        end
    end

Write Transformed Data to Transient Parameter#

Finally, the transformed data is written to the transient parameter. This makes the new data available within the session for visualization, analysis, or further processing. The timestamps ensure the data aligns correctly with the session timeline.

    sessionServiceClient.AddTimeDataToTransientParameter(
    sessionId,
    transientParameter.Identifier,
    timestamps2.ToArray(),
    values2.ToArray()
);

    sessionServiceClient.AddTimeDataToTransientParameter(
    sessionId,
    transient_parameter.Identifier,
    timestamps2,
    values2
)

    sessionServiceClient.AddTimeDataToTransientParameter( ...
    sessionId, ...
    transientParameter.Identifier, ...
    timestamps2, ...
    values2);
Image title
ATLAS Transient Parameter