Trunk compensation during reaching

Decomposes hand transport into trunk translation and arm-relative transport, and optionally computes signed axial trunk rotation from shoulder markers.

Usage

trunkCompensation(
  trunk,
  hand,
  shoulder_r = NULL,
  shoulder_l = NULL,
  reach_axis = NULL,
  vertical_axis = 3L,
  onset = NULL,
  offset = NULL
)

Arguments

trunk, hand

Numeric n by 3 position matrices in a common coordinate frame and unit.

shoulder_r, shoulder_l

Optional right and left shoulder position matrices used for axial rotation. Supply both or neither.

reach_axis

Optional length-3 reach-direction vector. The net hand displacement is used by default.

vertical_axis

Index (1, 2, or 3) of the vertical coordinate axis.

onset, offset

Optional 1-based sample bounds.

Value

A trunk_compensation object containing trunk, hand, and arm transport, trunk contribution, signed rotation in degrees, and reach axis.

References

Cirstea MC, Levin MF (2000). Compensatory strategies for reaching in stroke. Brain, 123:940-953. doi:10.1093/brain/123.5.940

Examples

hand <- cbind(seq(0, 0.4, length.out = 20), 0, 0)
trunk <- cbind(seq(0, 0.1, length.out = 20), 0, 0)
trunkCompensation(trunk, hand)
#> <trunk_compensation>
#>   hand: 0.4  trunk: 0.1  arm: 0.3
#>   trunk contribution: 0.250  rotation: NA deg