MAL.Velocity

ref_arr_out = MAL.Velocity( [BYREF arr_out      AS ARRAY],

                             BYREF arr_in       AS ARRAY,

                            [BYVAL nLength      AS INTEGER=2],

                            [BYVAL nPoint       AS INTEGER=ML_ALL],

                            [BYVAL nFrameOffset AS INTEGER=0] ) AS REFERENCE

Calculates the velocity of the data supplied in the input array.  The nLength parameter determines the number of frames it skips over for the velocity calculation.  This creates a way of applying a smoothing filter to the data.  The longer the length, the smoother the data.  The default is 2, meaning it's skipping 1 sample for each calculation. See table below.

To set the Frame rate  (fequency) used to calculate the velocity, call the MAL.FrameRate function.

Table Showing Frames used with nLength 2

Example:

OPTION EXPLICIT ON

OPTION BASE 1

' Include C3D Support

$INCLUDE "MyBASIC2_C3DFile"

$LIBRARY "MyBASIC2_C3DFileLib"

' Needed to extract and Display Version

$LIBRARY "MyBASIC2_ExtLib"

' Include the MaxMAL Library

$INCLUDE "MyBASIC2_MaxMAL"

$LIBRARY "MyBASIC2_MaxMALLib"

' Forward Declare PrintArray and DisplayVersion

DECLARE SUB PrintArray

DECLARE SUB DisplayVersion

' Declare variables and arrays

DIM nPoints AS INTEGER

DIM nFrames AS INTEGER

DIM hFile   AS INTEGER

' Test File

CONST cFileName = "e:\walk8.c3d"

' Display the current Library Version

CALL DisplayVersion()

' Open the Test File

hFile = C3DFile.Open( cFileName )

IF NOT hFile > 0 THEN

  PRINT "Error Opening File ";cFileName,

  STOP

ENDIF

' Get the no of points and frames

nFrames = C3DFile.GetNoOfFrames( hFile )

nPoints = C3DFile.GetNoOfPoints( hFile )

' Dimension the arrays

DIM Position(nFrames,nPoints,3)    AS REAL

DIM Velocity(nFrames,nPoints,3)     AS REAL

DIM Acceleration(nFrames,nPoints,3) AS REAL

' Get the Point Coordinates from C3D file

IF C3DFile.GetPoints( hFile, Position ) <> nFrames THEN

  C3DFile.Close( hFile )

  PRINT "Error Reading ";nPoints;" from file ";cFileName,

  STOP

ENDIF

' Set the Frame Rate to use in the MaxMAL Library

MAL.FrameRate( C3DFile.GetFrameRate( hFile ) )

' Display the Position Coordinates

CALL PrintArray( REF( Position ) )

' Calculate and Display Velocity

MAL.Velocity( Velocity, Position )

CALL PrintArray( REF( Velocity ) )

' Calculate and Display Acceleration

MAL.Acceleration( Acceleration, Position )

CALL PrintArray( REF( Acceleration ) )

' Close File

C3DFile.Close( hFile )

END

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

' Print an array with up to 3 dimensions.  Array is passed as a reference

'

SUB PrintArray( arr AS REFERENCE )

  RUN( "ArrayTable", arr, TRUE )

END SUB

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

' Display the MaxMAL Extension Library Version

'

SUB DisplayVersion()

  DIM major AS INTEGER

  DIM minor AS INTEGER

  DIM build AS INTEGER

  DIM qfe   AS INTEGER

  major = BYTE.HI( WORD.HI( MAL.Version() ) )

  minor = BYTE.LO( WORD.HI( MAL.Version() ) )

  build = BYTE.HI( WORD.LO( MAL.Version() ) )

  qfe   = BYTE.LO( WORD.LO( MAL.Version() ) )

  PRINT "Library Version: ";FORMAT( "%d, %d, %d, %d", major, minor, build, qfe ),

  PRINT "Option Flags:    ";FORMAT( "0x%08X", MAL.Version( TRUE ) ),

END SUB