Table of Contents
Metric Dot Product
Overview
This command creates a dot product of two metric vectors, it can be used to calculate helpful values like angles and work. The command acts on the active files. The Metric Dot Product command can be found in the Pipeline Workshop under the Metric folder.
Pipeline Command
Metric_Dot_Product ! /RESULT_FILE= ! /RESULT_METRIC_FOLDER=PROCESSED /RESULT_METRIC_NAME= ! /METRIC1_FILE= ! /METRIC1_FOLDER=PROCESSED /METRIC1_NAME= ! /METRIC2_FILE= ! /METRIC2_FOLDER=PROCESSED /METRIC2_NAME= ! /DIVIDE_BY_METRIC2_LENGTH=TRUE ! /GENERATE_MEAN_AND_STDDEV=TRUE ! /APPEND_TO_EXISTING_VALUES=FALSE ! /RETAIN_NO_DATA_VALUES=FALSE ;
Command Parameters
The following table shows the command parameters seen above and their descriptions:
| RESULT_FILE | The file type of the result |
| RESULT_METRIC_FOLDER | The name of the result signal folder |
| RESULT_METRIC_NAME | The name of the result signal |
| METRIC1_FILE | The movement trial containing the first metric value |
| METRIC1_NAME | The name of the signal containing the first metric value |
| METRIC1_FOLDER | The name of the metric signal folder |
| DIVIDE_BY_METRIC2_LENGTH | (True or False) Divide the resulting signal by the length of the second metric |
| GENERATE_MEAN_AND_STDDEV | (True or False)Generate the mean and standard deviation for all of the metrics created |
| APPEND_TO_EXISTING_VALUES | (True or False)Append this list of metrics to an existing metric of the same result name |
| RETAIN_NO_DATA_VALUES | In cases where there is NO_DATA at an event, you need to specify the parameter /Retain_No_Data_Values=TRUE should you want this included in the resulting signal. |
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.
The dialog box allows you to assign values to the command parameters outlined above.
Metric_File
If Metric1_File or Metric2_File are empty, Visual3D uses each active file when processing the command.
These parameters exist because the user may want to compute the dot product relative to a signal in the GLOBAL workspace or a specified file.
Divide_By_Metric2_Length
When this is true, a unit vector of Metric2 is used.
Append_to_Existing_Values
The results are concatenated to an existing signal.
Example: Computing Step Length from Stride Vectors Using Dot Product
In this example the Metric Dot Product command is used along with Metric Vector Between Events and Automatic Gait Events to find the length of each left foot step in a gait trial.
First all files are selected as active and key gait events are defined for each trial:
Select_Active_File /FILE_NAME=ALL_FILES ; Automatic_Gait_Events ! /FRAME_WINDOW=8 ! /USE_TPR=TRUE ! /TPR_EVENT_INSTANCE=1 ;
Next Metric Vector Between Events is used twice to define vectors for the proximal end of the left foot between gait events:
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=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 ;
Now that the vectors for the left foot have been defined, Metric Dot Product can be used to compute the dot product of those vectors and determine the left step length for each stride:
Metric_Dot_Product ! /METRIC1_FILE= /METRIC1_NAME=LeftStep ! /METRIC1_FOLDER=PROCESSED ! /METRIC2_FILE=GLOBAL /METRIC2_NAME=StrideVectors_MEAN ! /METRIC2_FOLDER=PROCESSED /RESULT_METRIC_NAME=LeftStepLength ! /RESULT_METRIC_FOLDER=PROCESSED ! /DIVIDE_BY_METRIC2_LENGTH=TRUE /GENERATE_MEAN_AND_STDDEV=TRUE ! /APPEND_TO_EXISTING_VALUES=FALSE ;
The METRIC:PROCESSED folder should now contain several new metrics including 3= values (vector, mean, and std dev) for both StrideVectors and LeftStepLength. The results should look similar to below:
A more complete example including dot products is available here.