eseis (version 0.6.0)

signal_spectrogram: Calculate spectrograms (power spectral density estimates) from time series.

Description

This function creates spectrograms from seismic signals. It supports the standard spectrogram approach, multitaper, and the Welch method.

Usage

signal_spectrogram(
  data,
  time,
  dt,
  Welch = FALSE,
  window,
  overlap = 0.5,
  window_sub,
  overlap_sub = 0.5,
  method = "periodogram",
  nw = 4,
  k = 7,
  n_cores = 1,
  plot = FALSE,
  ...
)

Value

List with spectrogram matrix, time and frequency vectors.

Arguments

data

Numeric vector or list of vectors, seismic signal to be processed.

time

POSIX.ct vector with time values. If omitted, an artificial time vector will be created, based on dt. Only needed if data is no eseis object.

dt

Numeric value, sampling period. If omitted, either estimated from time or set to 0.01 s (i.e., f = 100 Hz). Only needed if data is no eseis object.

Welch

Logical value, option to use the Welch method for calculations.

window

Numeric value, time window length in seconds used to calculate individual spectra. Set to 1 percent of the time series length by default.

overlap

Numeric value, fraction of window overlap.

window_sub

Numeric value, length of the sub-window in seconds used to calculate spectra. Only relevant if Welch = TRUE. If omitted, the sub-window length is set to 10 percent of the main window length.

overlap_sub

Numeric value, fraction of sub-window overlap.

method

Character value, method to calculate the spectra. One out of "periodogram", "autoregressive" and "multitaper". Default is "periodogram".

nw

Numeric value, multitaper time-bandwidth parameter, default is 4.0.

k

Numeric value, multitaper number of tapers, default is 7.

n_cores

Numeric value, number of CPU cores to use. Disabled by setting to 1. Default is 1.

plot

Logical value, toggle plot output. Default is FALSE. For more customised plotting see plot_spectrogram.

...

Additional arguments passed to the function.

Author

Michael Dietze

Details

Data containing NA values is replaced by zeros and set to NA in the output data set.

See Also

spectrum, spec.pgram, spec.mtm

Examples

## load example data set
data("earthquake")

## calculate and plot PSD straight away
P <- signal_spectrogram(data = s$BHZ, 
                               time = t, 
                               dt = 1 / 200, 
                               plot = TRUE)

## calculate and plot PSD with defined window sizes and the Welch method
P <- signal_spectrogram(data = s$BHZ, 
                               time = t, 
                               dt = 1 / 200, 
                               window = 5, 
                               overlap = 0.9, 
                               window_sub = 3, 
                               overlap_sub = 0.9, 
                               Welch = TRUE,
                               plot = TRUE)
                               
## calculate and plot PSD with even smaller window sizes, the Welch
## method and using multitapers, uncomment to use.
# P <- signal_spectrogram(data = s$BHZ, 
#                                time = t, 
#                                dt = 1 / 200, 
#                                window = 2, 
#                                overlap = 0.9, 
#                                window_sub = 1, 
#                                overlap_sub = 0.9, 
#                                Welch = TRUE,
#                                method = "multitaper",
#                                plot = TRUE)