Expression Items

Data_Tree

Signals should be placed into the expression in the form:

SIGNAL_TYPE::SIGNAL_FOLDER::SIGNAL_NAME

To define a specific element of a signal (e.g. the X Component)

SIGNAL_TYPE::SIGNAL_FOLDER::SIGNAL_NAME::X

To define a specific frame of a data of signal (e.g. Frame 2)

SIGNAL_TYPE::SIGNAL_FOLDER::SIGNAL_NAME[2]

Data stored in the GLOBAL Workspace should be expressed as follows:

GLOBAL::SIGNAL_TYPE::SIGNAL_FOLDER::SIGNAL_NAME

NOTE: Global signals can be accessed regardless of the ACTIVE FILES.

Examples for Specifying a Data Tree Signal

TARGET::ORIGINAL::RFT1 = Signal RFT1 in the TARGET type and ORIGINAL folder

ANALOG::PROCESSED::FX1 = Signal FX1 in the ANALOG type and PROCESSED folder

PARAMETER::ANALOG::RATE= Parameter RATE in the ANALOG group of the C3D PARAMETERS

Model_Builder

Model metrics have a simpler syntax. The Signal Type and Signal Folder need not be specified because there is only one version of a signal.

Creating a Landmark at the center of a ball

Given 6 markers placed on the surface of a round ball

BALL1, BALL2, BALL3, BALL4, BALL5, BALL6

Create a model metric at the center of a best fit sphere to the ball.

Metric Name= BALL

Metric Expression = Best_Fit_Sphere(List(BALL1, BALL2, BALL3, BALL4, BALL5, BALL6))

The resulting metric will have 3 values separated by a comma (e.g. the 3 components of the center)

As an example a center value of (0.5, 0.6, 0.7) would appear as

0.5,0.6,0.7

Create a landmark using this metric data

Note the syntax for the offsets

BALL[1,1]

The syntax may seem a little strange, but [1,1] refers to the first element of the first frame