findpeaks

Find peaks (maxima) in a time series. This function is modified from pracma::findpeaks.

findpeaks(
  x,
  IsDiff = TRUE,
  nups = 1,
  ndowns = nups,
  zero = "0",
  peakpat = NULL,
  minpeakheight = -Inf,
  minpeakdistance = 1,
  y_min = 0,
  y_max = 0,
  npeaks = 0,
  sortstr = FALSE,
  IsPlot = F
)

Arguments

x	Numeric vector.
IsDiff	If want to find extreme values, IsDiff should be true; If just want to find the continue negative or positive values, just set IsDiff as false.
nups	minimum number of increasing steps before a peak is reached
ndowns	minimum number of decreasing steps after the peak
zero	can be +, -, or 0; how to interprete succeeding steps of the same value: increasing, decreasing, or special
peakpat	define a peak as a regular pattern, such as the default pattern [+]{1,}[-]{1,}; if a pattern is provided, the parameters nups and ndowns are not taken into account
minpeakheight	The minimum (absolute) height a peak has to have to be recognized as such
minpeakdistance	The minimum distance (in indices) peaks have to have to be counted. If the distance of two maximum extreme value less than minpeakdistance, only the real maximum value will be left.
y_min	Threshold is defined as the difference of peak value with trough value. There are two threshold (left and right). The minimum threshold should be greater than y_min.
y_max	Similar as y_min, The maximum threshold should be greater than y_max.
npeaks	the number of peaks to return. If sortstr = true, the largest npeaks maximum values will be returned; If sortstr = false, just the first npeaks are returned in the order of index.
sortstr	Boolean, Should the peaks be returned sorted in decreasing oreder of their maximum value?
IsPlot	Boolean.

Examples

x <- seq(0, 1, len = 1024)
pos <- c(0.1, 0.13, 0.15, 0.23, 0.25, 0.40, 0.44, 0.65, 0.76, 0.78, 0.81)
hgt <- c(4, 5, 3, 4, 5, 4.2, 2.1, 4.3, 3.1, 5.1, 4.2)
wdt <- c(0.005, 0.005, 0.006, 0.01, 0.01, 0.03, 0.01, 0.01, 0.005, 0.008, 0.005)
pSignal <- numeric(length(x))
for (i in seq(along=pos)) {
    pSignal <- pSignal + hgt[i]/(1 + abs((x - pos[i])/wdt[i]))^4
}

plot(pSignal, type="l", col="navy"); grid()
x <- findpeaks(pSignal, npeaks=3, y_min=4, sortstr=TRUE)
points(val~pos, x$X, pch=20, col="maroon")