Movement-path straightness

The straightness of a movement trajectory: the ratio of the straight-line (direct) distance between the first and last points to the travelled path length. A straight reach scores 1; a curved or decomposed path scores below 1. The reciprocal (index of curvature) grows with path irregularity, a hallmark of limb ataxia.

Usage

pathStraightness(trajectory)

Arguments

trajectory

Numeric matrix of positions over time (rows = samples, columns = 1-3 spatial axes), or a numeric vector for a single axis.

Value

A list: path_length, direct_distance, straightness (direct / path, in (0, 1]) and index_of_curvature (path / direct, >= 1).

See also

reachingKinematics(), limbAtaxiaIndex()

Examples

pathStraightness(cbind(c(0, 0, 1), c(0, 1, 1)))$straightness   # L-path
#> [1] 0.7071068