Arrays

MyBASIC2 Arrays

The Motion Analysis Library uses MyBASIC2 arrays of REAL to store and process the data.  A MyBASIC2 array can have up to 4 dimensions.  To dimension an array, use the DIM statement.  The Motion Analysis Library uses 3 of the 4 dimensions.  The 4 MyBASIC2 dimensions are numbered as:

( dim1, dim2, dim3, dim4 )

The dimensions are used as the following in the Motion Analysis Library:

dim1   Not Used by MAL

dim2   No of Frames

dim3   No of Points or Channels

dim4   Data Dimension (1, 2, 3 or 5 for C3D with Residual and Camera Mask)

DIM data( Frames, Points, DataDimension ) AS REAL

If one or more dimensions only have one element, then you can omit them from right to left.  For instance, an array with 1D data can be dimensioned as

DIM data( Frames, Points ) AS REAL

This is the same as

DIM data( Frames, Points, 1 ) AS REAL

Subsequently, data with only 1 dimension such as analog data and only one point or channel can be specified as

DIM data( Frames ) AS REAL

This is the same as declaring the array as

DIM data( Frames, 1, 1 ) AS REAL

Arrays with 2D/3D data and only one point may be declared and used as

DIM data( Frames, 2 ) AS REAL

DIM data( Frames, 3 ) AS REAL

When single point output arrays are dynamically created, it will use this alternate format.  These can then be used as input arrays in function call that require 2D or 3D data as input.

To initialize or assign array values using MyBASIC2, please see LET statement.  You can also use the MAL.Set function to assign an array a value or using another array.  The advantage of using MAL.Set is that it returns a reference that can be used as a parameter in another function call.  It can also also assign ranges of frames and/or points/channels.

To specify a subscript of an array in MyBASIC2 you use indexes (indices).  The indexes are numbered from right to left as opposed to the dimensions.  To access an element of an array with 3 dimensions, index 1 will specify the data index, index 2 specifies point/channel and index 3 is the frame number.  Index 4 is currently not being used.  Note that indexes are all based on current OPTION BASE setting.

Indexes are specified as Array( ix4, ix3, ix2, ix1 ) and is the same as Array( NotUsed, Frame, Point, DataDimension ).

ix4 - Not Used by MAL

ix3 - Frames

ix2 - Points or Channels.

ix1 - Data Dimension (1D, 2D or 3D).

Frame Offsets and Points or Channels

Most functions in the MaxMAL Library accepts a Point or Channel number.  These are always specified with 1 being the first point/channel.  You can also specify a range of points/channels by using PTS( from, to ) where PTS( 1, 4 ) specifies point/channel 1 through 4.  To specify all points/channels, use the ML_ALL constant.

Frame Offsets are always specified starting at 0, i.e. no offset.  You can specify a range of frames using FRS( frame_offset, no_of_frames ).

Vector Index Arrays

A Vector Index Array (VIXA) is an INTEGER that contains compressed indexes into an array.  Only index 1, 2 and 3 are being represented.  The VIXA is formatted as:

ix3 - Frames

ix2 - Points or Channels.  Default 1

ix1 - Data Dimension (1D, 2D or 3D).  Default 1D

Functions that accepts a VIXA are functions that can use/specify a data dimension as well as points/channels and frame number.  You can use the VIX function to create a VIXA.  The VIX function uses the current OPTION BASE setting while VIXAs are always specified as base 0.  For example, VIXA 0 is will always specify first data dimension (X), first point/channel and the first frame.  Please see VIX function for more information.