Metric Event Sequence Count

Metric Event Sequence Count Creates a metric containing the number of Event Sequences. When a movement or series of movements (like a jump) is defined by an event sequence this command can be used to count the number of repetitions of that movement. The command can be found within the Pipeline Workshop under Metric.

Metric_Event_Sequence_Count
! /RESULT_METRIC_FOLDER=The resulting folder of the metric
/RESULT_METRIC_NAME= The resulting name of the metric
/TIME_INTERVAL= The number of event sequences which occur within a time interval
/EVENT_SEQUENCE= The event sequence to search for and count
/EXCLUDE_EVENTS= Don't count a sequence that contains this event
! /GENERATE_COUNT_TOTAL_IN_GLOBAL=
;

The following table shows the command parameters and descriptions:

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.

The dialog box allows you to assign values to the command parameters outlined above.

The Time_Interval parameter can be used to count the number of events that occur within a specific interval.

If a trial is 20 seconds long, and a 5.0 second interval is specified, the result will be 4 metrics. Each metric will contain the number of event sequences which occur within each 5.0 second window.

Metric_Event_Sequence_Count
! /RESULT_METRIC_FOLDER= PROCESSED
/RESULT_METRIC_NAME= LSWING_COUNT_INT
/TIME_INTERVAL= 5.0
/EVENT_SEQUENCE= The event sequence to search for and count
/EXCLUDE_EVENTS= Don't count a sequence that contains this event
! /GENERATE_COUNT_TOTAL_IN_GLOBAL= Create a global count over the active files
;

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As a subject moves through the gait cycle the angular velocities of their joints and limbs follow a known sequence with each stride. For this example we will identify this sequence for the right shank and use Metric Event Sequence Count to approximate the number of strides in a trial.

As a subject walks or runs their knees go through an alternating cycle of flexion and extension. This can be seen through many measurements, including the X component angular velocity of their shank. Here we use the Event Threshold command to identify each time that the angular velocity of the subject's right shank crosses 0 and goes from negative to positive or vice versa.

Event_Threshold
/RESULT_EVENT_NAME=RSK_Positive
/SIGNAL_TYPES=KINETIC_KINEMATIC
/SIGNAL_FOLDER=RSK
/SIGNAL_NAMES=AngVel
/SIGNAL_COMPONENTS=X
! /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=0
/ON_ASCENT=TRUE
/ON_DESCENT=FALSE
! /FRAME_WINDOW=8
! /ENSURE_FRAMES_BEFORE=FALSE
! /ENSURE_FRAMES_AFTER=FALSE
;

Event_Threshold
/RESULT_EVENT_NAME=RSK_Negative
/SIGNAL_TYPES=KINETIC_KINEMATIC
/SIGNAL_FOLDER=RSK
/SIGNAL_NAMES=AngVel
/SIGNAL_COMPONENTS=X
! /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=0
/ON_ASCENT=FALSE
/ON_DESCENT=TRUE
! /FRAME_WINDOW=8
! /ENSURE_FRAMES_BEFORE=FALSE
! /ENSURE_FRAMES_AFTER=FALSE
;

Now, using these events we can use Metric Event Sequence Count to count the number of instances in which the right knee goes from flexing into extending and back again, with each of these representing one stride.

Metric_Event_Sequence_Count
! /RESULT_METRIC_FOLDER=PROCESSED
/RESULT_METRIC_NAME=RSK_flexion_extension
! /TIME_INTERVAL=
/EVENT_SEQUENCE=RSK_Positive+RSK_Negative
/EXCLUDE_EVENTS=
! /GENERATE_COUNT_TOTAL_IN_GLOBAL=TRUE
;

A new folder should now be present in the METRIC folder containing a count of the event sequence. This number corresponds to the number of strides taken in a trial, which can be confirmed through further analysis or by watching the trial simulation.