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Short-Time Fourier Transform for EEG

Source: R/eeg-timefreq.R
eegSTFT.Rd

Computes the Short-Time Fourier Transform (STFT) spectrogram for multi-channel EEG data. Uses a sliding window with configurable overlap and window function to produce a time-frequency power representation.

Usage

eegSTFT(
  x,
  window_sec = 0.5,
  overlap = 0.75,
  window_type = c("hanning", "hamming", "rectangular"),
  assay_name = NULL,
  output_assay = "stft_power"
)

Arguments

x

A PhysioExperiment object with EEG data (2D: time x channels).

window_sec

Window length in seconds (default: 0.5).

overlap

Overlap fraction between adjacent windows, from 0 to 1 exclusive (default: 0.75).

window_type

Window function to apply: "hanning", "hamming", or "rectangular" (default: "hanning").

assay_name

Name of the input assay. If NULL, the default assay is used.

output_assay

Name the result is stored under. Despite the argument's name this is a key in metadata, NOT an assay: after the call assay(x, "the value given") does not exist while metadata(x)$the value given holds the result (default: "the value given"). (default: "stft_power").

Value

Modified PhysioExperiment with:

  • 3D power array (time_bins x frequencies x channels) in output_assay

  • Time bin centers, frequency vector, and parameters in metadata(x)$stft, a list containing time_axis, freq_axis, window_sec, overlap, window_type, window_length, and hop_size

References

Tallon-Baudry, C., et al. (1997). Oscillatory gamma-band activity during conscious perception. Trends in Cognitive Sciences, 3(4), 151-162.

See also

eegMorletWavelet(), eegMultitaper(), eegPlotSpectrogram()

Examples

pe <- make_eeg(n_time = 2000, n_channels = 4, sr = 250)
pe_stft <- eegSTFT(pe, window_sec = 0.5, overlap = 0.75)
# results are stored in metadata(x)$stft
str(S4Vectors::metadata(pe_stft)$stft, max.level = 1)
#> List of 7
#>  $ time_axis    : num [1:59] 0.252 0.38 0.508 0.636 0.764 ...
#>  $ freq_axis    : num [1:64] 0 1.98 3.97 5.95 7.94 ...
#>  $ window_sec   : num 0.5
#>  $ overlap      : num 0.75
#>  $ window_type  : chr "hanning"
#>  $ window_length: int 126
#>  $ hop_size     : int 32