====== Subtract Signals ======

Subtract the components of the specified signals.

**Note: Signals must be at the same sampling rate. If your signals are a different rate, you can use the [[Visual3D:Documentation:Pipeline:Expressions:Expressions_Overview|Evaluate_Expression]] command, which determines an appropriate rate automatically.**

The command can be edited via text editor and dialog. The details on the dialog and command are found below:

|{{:Subtract_Signals.png}}  |<code>\\ Subtract_Signals\\ /Signal_Types=The type of signal to be evaluated\\ /Signal_Names=The name of the signal to be evaluated\\ /Signal_Folder=The name of the signal folder\\ /Result_Folder= The name of the resulting folder\\ /Result_Names=The name of the resulting signal \\ /COMPONENT_SEQUENCE= The component (X,Y.Z) of the signal to be used.\\ </code>  |


----

==== Examples ====

Here you will find three examples:

=== Example 1: Subtract two target signals ===

<code>
!***********************************
! Distance between heel markers
!*********************************** 

Subtract_Signals
/SIGNAL_TYPES=TARGET+TARGET
/SIGNAL_NAMES=LHEE+RHEE
/SIGNAL_FOLDER=PROCESSED+PROCESSED
/RESULT_NAME=Heel_Distance
! /RESULT_FOLDER=PROCESSED
;
</code>

=== Example 2: Subtract a signal and a metric ===

<code>
!******************************************************
! Take the vertical GRF, subtract the body weight, and divide the result by body mass to
! get the vertical CoM acceleration
!******************************************************
</code>

<code>
! Add the two signals from F1 and F2 - end result is GRF for both plates
Add_Signals
/SIGNAL_TYPES=FORCE+FORCE
/SIGNAL_NAMES=FP1+FP2
/SIGNAL_FOLDER=PROCESSED+PROCESSED
/RESULT_NAME=GRF
/RESULT_FOLDER=PROCESSED
;

! Subtract the body weight in N
Subtract_Signals
/SIGNAL_TYPES=DERIVED+METRIC
/SIGNAL_FOLDER=PROCESSED
/SIGNAL_NAMES=GRF+MASS_N
/COMPONENT_SEQUENCE=Z, ALL
/RESULT_NAME=GRF_R
! /RESULT_FOLDER=PROCESSED
;

! Divide the result by body mass to get the vertical CoM acceleration
Divide_Signals
/SIGNAL_TYPES=DERIVED+METRIC
/SIGNAL_FOLDER=PROCESSED
/SIGNAL_NAMES=GRF_R+MASS
/COMPONENT_SEQUENCE=ALL
/RESULT_NAME=COM_GRF_Z_ACCEL
! /RESULT_FOLDER=PROCESSED
;
</code>

=== Example 3: Subtract two metrics ===

<code>
!******************************************************
! Subtract two metrics to calculate Leg length
!******************************************************
! Mean for Left Medial Ankle Standing Height
Metric_Mean
/RESULT_METRIC_NAME=LMMA_Height
! /APPLY_AS_SUFFIX_TO_SIGNAL_NAME=FALSE
! /RESULT_METRIC_FOLDER=PROCESSED
/SIGNAL_TYPES=TARGET
/SIGNAL_NAMES=L_MANK
/SIGNAL_FOLDER=PROCESSED
/SIGNAL_COMPONENTS=Z
/EVENT_SEQUENCE=
/EXCLUDE_EVENTS=
/GENERATE_MEAN_AND_STDDEV=FALSE
! /APPEND_TO_EXISTING_VALUES=FALSE
;

! Mean for Right Medial Ankle Standing Height
Metric_Mean
/RESULT_METRIC_NAME=RMMA_Height
! /APPLY_AS_SUFFIX_TO_SIGNAL_NAME=FALSE
! /RESULT_METRIC_FOLDER=PROCESSED
/SIGNAL_TYPES=TARGET
/SIGNAL_NAMES=R_MANK
/SIGNAL_FOLDER=PROCESSED
/SIGNAL_COMPONENTS=Z
/EVENT_SEQUENCE=
/EXCLUDE_EVENTS=
/GENERATE_MEAN_AND_STDDEV=FALSE
! /APPEND_TO_EXISTING_VALUES=FALSE
;

! Left Leg Length - Distance between LASIS and LMMA heights 
Subtract_Signals
/SIGNAL_TYPES=METRIC+METRIC
/SIGNAL_NAMES=LASIS_Height+LMMA_Height
/SIGNAL_FOLDER=PROCESSED+PROCESSED
/RESULT_NAME=Left_Leg_Length
! /RESULT_FOLDER=PROCESSED
;
</code>