Table of Contents
Event Threshold
Overview
The Event_Threshold command is used to detect threshold crossings (when signal crosses a specified value) in biomechanical signals and label events accordingly. This command provides extensive control over event placement by allowing users to define frame or time offsets, include or exclude sequences, and refine detections using component selection and event constraints.
This command is particularly useful for defining critical events based on signal thresholds, such as peak force occurrences, velocity changes, or acceleration-based triggers.
Note: The threshold parameter specified can be a number, a PROCESSED METRIC, or an expression.
Pipeline Command
The command below is as seen on the Visual3D application, it has many parameters as there are many options to manipulate this command.
Event_Threshold /RESULT_EVENT_NAME= ! /SIGNAL_TYPES= ! /SIGNAL_FOLDER=ORIGINAL ! /SIGNAL_NAMES= ! /SIGNAL_COMPONENTS= ! /FRAME_OFFSET=0 ! /TIME_OFFSET= ! /EVENT_SEQUENCE= ! /EXCLUDE_EVENTS= ! /EVENT_SEQUENCE_INSTANCE=0 ! /EVENT_SUBSEQUENCE= ! /SUBSEQUENCE_EXCLUDE_EVENTS= ! /EVENT_SUBSEQUENCE_INSTANCE=0 ! /EVENT_INSTANCE=0 ! /THRESHOLD= ! /ON_ASCENT= ! /ON_DESCENT= ! /FRAME_WINDOW=8 ! /ENSURE_FRAMES_BEFORE=FALSE ! /ENSURE_FRAMES_AFTER=FALSE ;
Command Parameters
The following table shows the command parameters and descriptions:
| Parameter | Description |
| /RESULT_EVENT_NAME= | The name assigned to the detected threshold event. |
| !/SIGNAL_TYPES= | The type of signal to evaluate (i.e. Analog, Link Model Based, etc.) |
| !/SIGNAL_FOLDER=ORIGINAL | The folder containing the signal. |
| !/SIGNAL_NAMES= | Specifies the signal to be analyzed. |
| !/SIGNAL_COMPONENTS= | Defines which signal components should be analyzed. |
| !/FRAME_OFFSET=0 | Shifts the event forward or backward by a specified number of frames. |
| !/TIME_OFFSET= | Shifts the event forward or backward by a specified time in seconds. |
| !/EVENT_SEQUENCE= | Sequence of events within which the command is performed (i.e. RHS + RHS). |
| !/EXCLUDE_EVENTS= | Events to be excluded from sequence. |
| !/EVENT_SEQUENCE_INSTANCE=0 | Which instance of an event sequence to use. |
| !/EVENT_SUBSEQUENCE= | Subsequence of events to analyze (i.e. LTO + LHS). |
| !/SUBSEQUENCE_EXCLUDE_EVENTS= | Events to exclude from the subsequence. |
| !/EVENT_SUBSEQUENCE_INSTANCE=0 | Instance of the event subsequence to analyze. |
| !/EVENT_INSTANCE= | Determines how many event occurrences to consider (0 for all, positive for sequential selection, negative for reverse selection). |
| !/THRESHOLD= | Threshold value to trigger event detection. |
| !/ON_ASCENT= | Determine if the event is detected when the signal crosses the threshold in an upward direction. |
| !/ON_DESCENT= | Determines if the event is detected when the signal crosses the threshold in a downward direction. |
| !/FRAME_WINDOW=8 | The range of frames that must satisfy the threshold crossing condition. |
| !/ENSURE_FRAMES_BEFORE=FALSE | (True or False) Radius frames of data before crossing must lie on the same side of the threshold. |
| !/ENSURE_FRAMES_AFTER=FALSE | (True or False) Radius frames of data after crossing must lie on the same side of the threshold. |
Dialog
The command can be edited in a text editor or in a dialog form. To edit in the dialog pop up form either click on the Edit button in the pipeline workshop or double-click on the pipeline command. The dialog is shown below.
Examples
The following examples will go through the use of the Event_Threshold command in the Visual3D application.
Example 1: Detecting Peak Ground Reaction Force
This example uses the Event_Threshold command to detect the event Max_GRF when the vertical ground reaction force (GRF_Z) crosses 1000N in the ascending direction:
Event_Threshold /RESULT_EVENT_NAME= Max_GRF /SIGNAL_TYPES=FORCE ! /SIGNAL_FOLDER=ORIGINAL /SIGNAL_NAMES=GRF_Z ! /SIGNAL_COMPONENTS= ! /FRAME_OFFSET=0 ! /TIME_OFFSET= ! /EVENT_SEQUENCE= ! /EXCLUDE_EVENTS= ! /EVENT_SEQUENCE_INSTANCE=0 ! /EVENT_SUBSEQUENCE= ! /SUBSEQUENCE_EXCLUDE_EVENTS= ! /EVENT_SUBSEQUENCE_INSTANCE=0 ! /EVENT_INSTANCE=0 /THRESHOLD= 1000 /ON_ASCENT= TRUE ! /ON_DESCENT= ! /FRAME_WINDOW=8 ! /ENSURE_FRAMES_BEFORE=FALSE ! /ENSURE_FRAMES_AFTER=FALSE ;
Example 2: Maintaining Event Window after Threshold Closing
In this example, the events FP3_Y and FP3_Y_ENSURE are created using the command. The event FP3_Y_ENSURE will use the “Ensure Window After” option within the dialog box, which guarantees that the event window remains open for a specified duration after the triggering condition is met.
To ensure correct functionality of the example, the following must be done:
- Import the SIGNAL_TYPE/FOLDER or enter these parameters manually into the text editor.
- Specify only one signal component at a time.
- One of either ON_ASCENT or ON_DESCENT must be selected, if neither option is selected then no events will be created. In this example, we will chose to label on Ascent.
Event_Threshold /RESULT_EVENT_NAME= FP3_Y /SIGNAL_TYPES= FORCE /SIGNAL_NAMES= FP3 ! /SIGNAL_FOLDER= ORIGINAL /SIGNAL_COMPONENTS= Y ! /FRAME_OFFSET= 0 ! /TIME_OFFSET= ! /EVENT_SEQUENCE= ! /EXCLUDE_EVENTS= ! /EVENT_SEQUENCE_INSTANCE= 0 ! /EVENT_SUBSEQUENCE= ! /SUBSEQUENCE_EXCLUDE_EVENTS= ! /EVENT_SUBSEQUENCE_INSTANCE= 0 ! /EVENT_INSTANCE= 0 ! /SELECT_X= ! /SELECT_Y= ! /SELECT_Z= ! /SELECT_RESIDUAL= ! /START_AT_EVENT= ! /END_AT_EVENT= /THRESHOLD= 0.05 /ON_ASCENT= TRUE /ON_DESCENT= FALSE /FRAME_WINDOW= 25 /ENSURE_FRAMES_BEFORE= FALSE /ENSURE_FRAMES_AFTER= FALSE ; Event_Threshold /RESULT_EVENT_NAME= FP3_Y_ENSURE /SIGNAL_TYPES= FORCE /SIGNAL_NAMES= FP3 ! /SIGNAL_FOLDER= ORIGINAL /SIGNAL_COMPONENTS= Y ! /FRAME_OFFSET= 0 ! /TIME_OFFSET= ! /EVENT_SEQUENCE= ! /EXCLUDE_EVENTS= ! /EVENT_SEQUENCE_INSTANCE= 0 ! /EVENT_SUBSEQUENCE= ! /SUBSEQUENCE_EXCLUDE_EVENTS= ! /EVENT_SUBSEQUENCE_INSTANCE= 0 ! /EVENT_INSTANCE= 0 ! /SELECT_X= ! /SELECT_Y= ! /SELECT_Z= ! /SELECT_RESIDUAL= ! /START_AT_EVENT= ! /END_AT_EVENT= /THRESHOLD= 0.05 /ON_ASCENT= TRUE /ON_DESCENT= FALSE /FRAME_WINDOW= 25 /ENSURE_FRAMES_BEFORE= FALSE /ENSURE_FRAMES_AFTER= TRUE ;
Result
After running this pipeline, you will notice 3 events have been created:
- 2 instances of FP3_Y, crosses the threshold (0.05) two times during the trial.
- 1 instance of FP3_Y_ENSURE, crosses the threshold (0.05) and stays above the threshold for the frame window (25) one time during the trial.
Notes
Visual3D Versions supporting Subject Prefixes
When defining events for subjects that use a prefix to define the data belonging to that subject, event labels will also have the prefix of the subject the events belong to.
NOTE: When using events in a command, the commands will iterate across subjects contained in the current workspace. As such, events and sequences listed as command parameters should NOT contain a prefix. As each subject is processed, the event range/sequence specified will automatically use the specific events prefixed for each subject as they are processed.