Signal Commands Overview

Signal commands are used to manipulate signals within the Visual3D pipeline.

Signal Math

These commands perform mathematical operations using signals.

Command	Description
Evaluate_Expression	Can be used to flexibly define custom mathematical functions.
Add_Constant_To_Signals	Adds a constant to the specified components of a signal(s).
Add_Random_Noise_To_Signals	Adds random noise to the specified signal(s).
Add_Signals	Add the specified signals. Signals must be at the same sampling rate. If your signals are a different rate, you can use the Evaluate_Expression command, which determines an appropriate rate automatically.
Compute_Planar_Angle	This command computes a planar angle between three or four points.
Compute_Volume_Of_Chest_Wall	Compute the volume of the chest wall as described by Ferrigno et al., 1994.
Compute_Volume_Of_A_Convex_Hull	Compute the volume of the convex hull surrounding a set of (2D or 3D) vertices.
Divide_Signals	This command will divide signals with the first signal being the numerator.
Divide_Signal_By_Constant	This command will divide a specified components of a signal(s) by a constant.
First_Derivative	Compute the first derivative at each point of a signal. This command is useful for calculating the velocity of targets, landmarks, etc.
Second_Derivative	Compute the second derivative at each point of a signal. This command is useful for calculating the acceleration of targets, landmarks, etc.
Indefinite_Integral	Compute an indefinite integral from the start event to the stop event.
Multiply_Signals	Multiply the components of the specified signals.
Multiply_Signals_By_Constant	Multiply signals by a constant value.
Rectify	Take the absolute value of every element within a signal.
Signal_Magnitude	Calculate the magnitude of a signal according to: Magnitude=Sqrt( x^2+y^2+z^2 )
Subtract_Constant_From_Signals	Subtracts a constant from the specified components of a signal(s).
Subtract_Signals	Subtract the components of the specified signals.
Square_Root	Compute the square root of a signal or metric. This command can be used to compute the vector magnitude of a signal.

Signal/Data Management

These commands manage signals within the Visual3D workspace.

Command	Description
Create_Target	Add a new ORIGINAL TARGET to a C3D file.
Create_Targets_for_Base_of_Support	Add four ORIGINAL TARGET signals to a C3D file for the Base of Support.
Create_Rotation	Add a new ORIGINAL ROTATION signal to a C3D file.
Copy_Folder	Makes a copy of an existing folder. If the new folder already exists, select whether these signals should be overwritten (replaced).
Delete_Folder	Deletes the specified folder. Note that ORIGINAL folders can not be deleted.
Remove_Signals	Remove a signal from the Data Tree.
Remove_Unlabeled_Points	Vicon Nexus exports unlabeled trajectories identified with an asterisk (*) at the beginning of the filename; this command allows these to be removed.
Remove_Polygon_Signals	Remove processed signals generated by Polygon and stored as TARGET data in the C3D file.
Move_Polygon_Signals	Move TARGET signals generated by Polygon to the DERIVED data type.
Rename_Folder	Renames the specified folder.
Rename_Signals	Renames the specified signals.

Signal Filter

These commands apply filters to signals within the Visual3D workspace.

Command	Description
Average_Filter	Compute a signal where each resulting point is the average of the original signal within the specified filter window.
Quaternion_Average_Filter	Compute a signal that is a filtered quaternion signal using an algorithm provided by Synertial Inc.
Butterworth_Filter	Filter a signal using a digital lowpass (Butterworth) filter.
DFT_Filter	Compute a filter's DFT coefficients.
Onepass_Filter	One-pass, second order (BUTTERWORTH or CRITICALLY DAMPED) filter.
FFT_Filter	Filter (lowpass or highpass) a signal using a Fast Fourier Transform.
GCVSPL	A generalized, cross-validatory spline smoothing and differentation filter.
Lowpass Filter	Filter a signal using a digital lowpass (BUTTERWORTH or CRITICALLY DAMPED) filter.
Highpass Filter	Filter a signal using a digital highpass (BUTTERWORTH or CRITICALLY DAMPED) filter.
Moving_RMS	Calculate a linear envelope for a signal using the RMS of a moving window.
Median_Filter	Replace each point of a signal with the median value from a window centered on that point.
Shift_Frames	Shift a signal by adding or subtracting frames.
Teager_Kaiser_Energy	The Teager-Kaiser Energy Operator.

Signal Process

These commands process signals within the Visual3D workspace. For signal filters see the Signal Filter section of this page.

Command	Description
Compute_UD_Power	Compute unified deformable power at the distal end of the foot according to Takahashi, Kepple, and Stanhope (2012).
Distance_Along_Path	Calculate a signal's cumulative path distance.
Distance_Parallel_To_Path	Calculate a signal's parallel distance to a straight path.
Distance_Perpendicular_To_Path	Calculate a signal's perpindicular distance to a straight path.
Find_Representative_Signal	Find the representative signal of a set according to Shadmehr and Mussa-Ivaldi (1994).
Global_Normalized_Signal_Mean	Normalize a signal between events and calculate a global mean.
Command_Signal_Quality_Assurance	Perform signal QA using PCA scores.
Concatenate_Time_Normalized_Signals	Concatenate time-normalized signals between events.
Interpolate	Interpolate a signal's missing data points.
Merge_Data	This command merges data from more than one data name into a single one either by appending one signal to the end of another signal or by treating each original signal as a component of the new signal.
Replace	Replace missing data points of a signal.
Set_Data_To_New_Values	Set data to a specified replacement value, often NO_DATA.
Transform_Data_Coordinate_System	Transform a signal from one coordinate system to another.
Cross_Correlation	Computes the cross-correlation of two signals.
Compute_IK_Residuals	Computes the X, Y, and Z errors for each IK TARGET.

Examples

This wiki contains examples of how these signal commands can be used to accomplish common analytical tasks.

Compute the intersection of two lines (under construction)
Compute the intersection of a line with a plane (under construction)

The head fixation point is the intersection between the anterior direction of the head at one frame of time and an another frame of time. The head fixation point can be computed using the above example for the intersection of two lines.

HAS-Motion Software Documentation

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