Low-pass filter ground reaction force data

Applies low-pass filtering to force-plate signals. By default this uses a zero-phase Butterworth filter (requires the signal package). If signal is not available, the function falls back to a moving-average filter.

Usage

filterGRF(
  x,
  sampling_rate,
  cutoff = 20,
  order = 4,
  method = c("butterworth", "moving_average")
)

Arguments

x

Numeric vector or matrix (time x channels).

sampling_rate

Sampling rate in Hz.

cutoff

Low-pass cutoff frequency in Hz.

order

Butterworth filter order.

method

Filtering method: "butterworth" or "moving_average".

Value

Filtered data with the same dimensions as x.

References

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

See also

butterworthFilter() for general Butterworth filtering, analyzeForcePlate() for comprehensive force plate analysis.

Examples

sr <- 1000
t <- seq(0, 1, length.out = sr)
x <- sin(2 * pi * 10 * t) + 0.2 * sin(2 * pi * 150 * t)
y <- filterGRF(x, sampling_rate = sr, cutoff = 25)