# R/spectral_functions.R In nonlinearTseries: Nonlinear Time Series Analysis

#### Defines functions freq.spectrogramfreqtime.spectrogramplot.spectrogramspectrogram.zoospectrogram.tsspectrogram.defaultspectrogramblackmanhanninghamming

```# @export
hamming = function(n, alpha = 0.54, beta = 0.46){
alpha - beta * cospi (2 * (0:(n - 1)) / (n - 1))
}

# @export
hanning = function(n) {
0.5 * (1 - cospi( 2* (0:(n - 1)) / (n - 1)))
}

# @export
blackman = function(n, alpha = 0.16) {
a0 = (1 - alpha) / 2
a1 = 1 / 2
a2 = alpha / 2
a0 - a1 * cospi(2 * (0:(n - 1)) / (n - 1)) + a2 * cospi(4 * (0:(n - 1)) / (n - 1))
}

#' @import zoo
# @export
spectrogram = function(x, ...){
UseMethod("spectrogram")
}

# @export
spectrogram.default = function(x, width, by, pad = 0) {
if (width < 2) {
stop("width must be >= 2")
}
final_len = ifelse(n %% 2 == 0, n / 2 + 1, (n + 1) / 2)
(Mod(fft(c(x * hamming(width), rep(0,pad)))) ^ 2)[1:final_len]
}
spec = t(rollapply(x - mean(x), width = width, by = by,
time_spec = seq((width + 1) / 2, (width + 1) / 2 + (ncol(spec) - 1)* by, by = by)
freq_spec = seq(0, 0.5, length = nrow(spec))
# Create class
class(spec) = c("spectrogram", class(spec))
attr(spec,"freq") = freq_spec
attr(spec, "time") = time_spec
attr(spec, "width") = width
attr(spec, "by") = by
spec
}

# @export
spectrogram.ts = function(x, width, by, pad = 0) {
spec = spectrogram(as.numeric(x), width = width, by = by, pad = pad)
attr(spec,"freq") = attr(spec,"freq") * frequency(x)
attr(spec, "time") = attr(spec, "time") / frequency(x)
spec
}

# @export
spectrogram.zoo = function(x, width, by, pad = 0) {
}

# @export
plot.spectrogram = function(x, color.palette = terrain.colors,
xlab = "Time", ylab = "Frequency(Hz)",
main = "Spectrogram",
zlim = range(x, finite = TRUE),
trim = FALSE, ...) {
if (trim) {
x[which(x < zlim[[1]], arr.ind = T)] = zlim[[1]]
x[which(x > zlim[[2]], arr.ind = T)] = zlim[[2]]
}
filled.contour(attr(x, "time"), attr(x, "freq"), t(x),
color.palette = color.palette,
xlab = xlab, ylab = ylab, main = main,
zlim = zlim, ...)
}

# @export
time.spectrogram = function(x) {
attr(x, "time")
}

# @export
freq = function(x){
UseMethod("freq")
}

# @export
freq.spectrogram = function(x){
attr(x, "freq")
}
```

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nonlinearTseries documentation built on May 2, 2019, 5:47 p.m.