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Compute velocity from position data

Source: R/ops-derivatives.R
computeVelocity.Rd

Computes velocity (first derivative) from position assays in a PhysioExperiment object using finite differences.

Usage

computeVelocity(
  pe,
  assay_names = NULL,
  method = "central",
  sampling_rate = NULL
)

Arguments

pe

A PhysioExperiment object containing position assays.

assay_names

Character vector of assay names to differentiate. If NULL (default), auto-detects position_x/y/z or keypoint_x/y assays.

method

Finite difference method: "central" (default), "forward", or "backward".

sampling_rate

Sampling rate in Hz. If NULL (default), uses samplingRate(pe).

Value

PhysioExperiment with new velocity assays added. For 3D marker data, assays named velocity_x, velocity_y, velocity_z. For 2D keypoint data, assays named velocity_kp_x, velocity_kp_y.

References

Winter DA (2009). "Biomechanics and Motor Control of Human Movement." 4th ed. John Wiley & Sons.

See also

computeAcceleration() for second-order derivatives, computeSpeed() for scalar speed from velocity components, differentiate() for general-purpose numerical differentiation.

Examples

if (FALSE) { # \dontrun{
pe <- make_mocap_markers(n_time = 100, n_markers = 4, sr = 120)
pe <- computeVelocity(pe)
# velocity_x, velocity_y, velocity_z assays are now present
} # }