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--- visual3d:documentation:pipeline:metric_commands:metric_cross_product [2025/10/02 15:08] – [Examples] wikisysop
+++ visual3d:documentation:pipeline:metric_commands:metric_cross_product [2025/10/03 17:35] (current) – [Example: Computing Step Length from Stride Vectors Using Dot Product] wikisysop
@@ Line 63: / Line 63: @@
 The results are concatenated to an existing signal.
-====Examples====
+====Example: Computing Step Length from Stride Vectors Using Dot Product====
+In this example the **Metric Cross Product** command is used along with **Metric Vector Between Events** and **Automatic Gait Events** to find the width of each step in a gait trial.
-===Simple example: Step Width from  Stride Vectors===
+First all files are selected as active and key gait events are defined for each trial:
-Here we use the **Metric Cross Product** command to compute step width from previously calculated stride vectors found using **Metric Vector Between Events**.
-The command is as follows:
+<code>
+Select_Active_File
+/FILE_NAME=ALL_FILES
+;
+Automatic_Gait_Events
+! /FRAME_WINDOW=8
+! /USE_TPR=TRUE
+! /TPR_EVENT_INSTANCE=1
+;
+</code>
+Next **Metric Vector Between Events** is used twice for each side to define vectors for the proximal end of each foot between gait events:
+<code>
+Metric_Vector_Between_Events
+/START_SIGNAL_TYPE=KINETIC_KINEMATIC
+/START_SIGNAL_NAME=ProxEndPos
+/START_SIGNAL_FOLDER=LFT
+/END_SIGNAL_TYPE=KINETIC_KINEMATIC
+/END_SIGNAL_NAME=ProxEndPos
+/END_SIGNAL_FOLDER=LFT
+/EVENT_SEQUENCE=LHS+LHS
+/EXCLUDE_EVENTS=
+/METRIC_NAME=StrideVectors
+! /GENERATE_MEAN_AND_STDDEV=TRUE
+! /APPEND_TO_EXISTING_VALUES=FALSE
+! /GENERATE_VECTOR_LENGTH_METRIC=FALSE
+;
+Metric_Vector_Between_Events
+/START_SIGNAL_TYPE=KINETIC_KINEMATIC
+/START_SIGNAL_NAME=ProxEndPos
+/START_SIGNAL_FOLDER=RFT
+/END_SIGNAL_TYPE=KINETIC_KINEMATIC
+/END_SIGNAL_NAME=ProxEndPos
+/END_SIGNAL_FOLDER=RFT
+/EVENT_SEQUENCE=RHS+RHS
+/EXCLUDE_EVENTS=
+/METRIC_NAME=StrideVectors
+! /GENERATE_MEAN_AND_STDDEV=TRUE
+/APPEND_TO_EXISTING_VALUES=TRUE
+! /GENERATE_VECTOR_LENGTH_METRIC=FALSE
+;
+Metric_Vector_Between_Events
+/START_SIGNAL_TYPE=KINETIC_KINEMATIC
+/START_SIGNAL_NAME=ProxEndPos
+/START_SIGNAL_FOLDER=RFT
+/END_SIGNAL_TYPE=KINETIC_KINEMATIC
+/END_SIGNAL_NAME=ProxEndPos
+/END_SIGNAL_FOLDER=LFT
+/EVENT_SEQUENCE=RHS+LHS
+/EXCLUDE_EVENTS=
+/METRIC_NAME=LeftStep
+/GENERATE_MEAN_AND_STDDEV=FALSE
+! /APPEND_TO_EXISTING_VALUES=FALSE
+! /GENERATE_VECTOR_LENGTH_METRIC=FALSE
+;
+Metric_Vector_Between_Events
+/START_SIGNAL_TYPE=KINETIC_KINEMATIC
+/START_SIGNAL_NAME=ProxEndPos
+/START_SIGNAL_FOLDER=LFT
+/END_SIGNAL_TYPE=KINETIC_KINEMATIC
+/END_SIGNAL_NAME=ProxEndPos
+/END_SIGNAL_FOLDER=RFT
+/EVENT_SEQUENCE=LHS+RHS
+/EXCLUDE_EVENTS=
+/METRIC_NAME=RightStep
+/GENERATE_MEAN_AND_STDDEV=FALSE
+! /APPEND_TO_EXISTING_VALUES=FALSE
+! /GENERATE_VECTOR_LENGTH_METRIC=FALSE
+;
+</code>
+Now that the vectors for the feet have been defined, **Metric Cross Product** can be used to compute the dot product of those vectors and determine the step width for each stride:
 <code>
+! Calculate LeftStepWidth by taking cross product of LeftStep vector and StrideVectors_MEAN
+! Generate Mean and STD DEV
+Metric_Cross_Product
+! /METRIC1_FILE=
+/METRIC1_NAME=LeftStep
+! /METRIC1_FOLDER=PROCESSED
+/METRIC2_FILE=GLOBAL
+/METRIC2_NAME=StrideVectors_MEAN
+! /METRIC2_FOLDER=PROCESSED
+! /DIVIDE_BY_METRIC2_LENGTH=TRUE
+/RESULT_METRIC_NAME=LeftStepWidth
+! /RESULT_METRIC_FOLDER=PROCESSED
+! /GENERATE_MEAN_AND_STDDEV=TRUE
+! /APPEND_TO_EXISTING_VALUES=FALSE
+/GENERATE_VECTOR_LENGTH_METRIC=TRUE
+;
+! Calculate RightStepWidth by taking cross product of RightStep vector and StrideVectors_MEAN
+! Generate Mean and STD DEV
 Metric_Cross_Product
 ! /METRIC1_FILE=
@@ Line 87: / Line 182: @@
 </code>
-In the case that you already know or have calculated step length and know the associated stride vectors, the cross product can be used to compute step width.
+The **METRIC:PROCESSED** folder should now contain several new metrics including 3 values (vector, mean, and std dev) for right and left step width. The results should look similar to below:
-===Complex example===
-For a more in depth example similar to the one above go to [[visual3d:documentation:pipeline:signal_commands:mimicking_temporal_distance_command|this tutorial]].
+{{:visual3d:documentation:pipeline:metric_commands:left_step_width.png?600|}}{{:visual3d:documentation:pipeline:metric_commands:left_step_width_mean.png?600|}}
+A more complete example including dot products is available [[visual3d:documentation:pipeline:signal_commands:mimicking_temporal_distance_command|here]].