Skip to contents

Tremor power spectrum and dominant frequency

Source: R/movement-tremor.R
tremorSpectrum.Rd

Estimates the power spectrum of a movement signal (Welch periodogram) and summarises the tremor within a frequency band: the dominant frequency, its peak power, absolute and relative in-band power, the half-power bandwidth (peak sharpness) and the first-harmonic ratio.

Usage

tremorSpectrum(
  signal,
  sampling_rate,
  band = c(3, 12),
  detrend = TRUE,
  seg_sec = NULL
)

Arguments

signal

Numeric vector: one axis, or the vector magnitude, of an accelerometer / gyroscope / displacement signal (gravity removed for raw accelerometry).

sampling_rate

Sampling rate in Hz.

band

Length-2 tremor band c(low, high) in Hz (default c(3, 12)).

detrend

Remove the signal mean before spectral estimation (default TRUE; each Welch segment is also demeaned).

seg_sec

Optional Welch segment length in seconds (default: about an eighth of the record, rounded to a power of two).

Value

A list: dominant_freq_hz, peak_power, band_power_abs, band_power_rel (in-band / total power), half_power_bw_hz, harmonic_ratio (power at 2*f0 / power at f0), and the freq / psd vectors.

See also

tremorAmplitude(), tremorMetrics()

Examples

fs <- 100; t <- seq(0, 20, by = 1 / fs)
x <- 2 * sin(2 * pi * 5 * t)            # a 5 Hz, amplitude-2 tremor
tremorSpectrum(x, fs)$dominant_freq_hz
#> [1] 5.078125