make_specgram {tagtools}

Plot a spectrogram with default settings

Description

This is a wrapper function for specgram to draw a spectrogram with the same input argument names and defaults as the tag tools Matlab/Octave function make_specgram.

Usage

make_specgram(
  x,
  nfft = 256,
  fs = 2,
  window = signal::hanning(nfft),
  noverlap = length(window)/2,
  draw_plot = TRUE
)

Arguments

x

The input signal

nfft

specifies the number of frequency points used to calculate the discrete Fourier transforms.

fs

The sampling frequency in Hz

window

If you specify a scalar for window, make_specgram uses a Hanning window of that length. window must have length smaller than or equal to nfft and greater than noverlap.

noverlap

The number of samples the sections of x overlap.

draw_plot

(logical) Should a plot be drawn? Defaults to TRUE.

Value

if draw_plot is TRUE, a plot is produced. If it is FALSE, a list is returned, with as follows. Each element is a matrix and all three matrices are the same size.

• s, A matrix of spectrogram values of signal x in dB.

• f, Frequencies (Hz) corresponding to the rows of s

• t, Time indices corresponding to the columns of s

Examples

x <- signal::chirp(seq(from = 0, by = 0.001, to = 2),
  f0 = 0,
  t1 = 2,
  f1 = 500
)
fs <- 2
nfft <- 256
numoverlap <- 128
window <- signal::hanning(nfft)
S <- make_specgram(x, nfft, fs, window, numoverlap, draw_plot = FALSE)