findInflections: Find inflections

In soundgen: Sound Synthesis and Acoustic Analysis

Find inflections

Description

Finds inflections in discrete time series such as pitch contours. When there are no missing values and no thresholds, this can be accomplished with a fast one-liner like which(diff(diff(x) > 0) != 0) + 1. Missing values are interpolated by repeating the first and last non-missing values at the head and tail, respectively, and by linear interpolation in the middle. Setting a threshold means that small "wiggling" no longer counts. To use an analogy with ocean waves, smoothing (low-pass filtering) removes the ripples and only leaves the slow roll, while thresholding preserves only waves that are sufficiently high, whatever their period.

Usage

findInflections(x, thres = NULL, step = NULL, plot = FALSE, main = "")

Arguments

x	numeric vector with or without NAs
thres	minimum vertical distance between two extrema for them to count as two independent inflections
step	distance between values in s (only needed for plotting)
plot	if TRUE, produces a simple plot
main	plot title

Value

Returns a vector of indices giving the location of inflections.

Examples

x = sin(2 * pi * (1:100) / 15) * seq(1, 5, length.out = 100)
idx_na = c(1:4, 6, 7, 14, 25, 30:36, 39, 40, 42, 45:50,
           57, 59, 62, 66, 71:79, 98)
x[idx_na] = NA
soundgen:::findInflections(x, plot = TRUE)
soundgen:::findInflections(x, thres = 5, plot = TRUE)

for (i in 1:10) {
  temp = soundgen:::getRandomWalk(len = runif(1, 10, 100), rw_range = 10,
                                  rw_smoothing = runif(1, 0, 1))
  soundgen:::findInflections(temp, thres = 1, plot = TRUE)
  invisible(readline(prompt="Press [enter] to continue"))
}

soundgen documentation built on Sept. 29, 2023, 5:09 p.m.