findpeaks: Find Peaks

In pracma: Practical Numerical Math Functions

Find Peaks

Description

Find peaks (maxima) in a time series.

Usage

findpeaks(x, nups = 1, ndowns = nups, zero = "0", peakpat = NULL,
          minpeakheight = -Inf, minpeakdistance = 1,
          threshold = 0, npeaks = 0, sortstr = FALSE)

Arguments

x	numerical vector taken as a time series (no NAs allowed)
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, 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
threshold	the minimum
npeaks	the number of peaks to return
sortstr	logical; should the peaks be returned sorted in decreasing oreder of their maximum value

Details

This function is quite general as it relies on regular patterns to determine where a peak is located, from beginning to end.

Value

Returns a matrix where each row represents one peak found. The first column gives the height, the second the position/index where the maximum is reached, the third and forth the indices of where the peak begins and ends — in the sense of where the pattern starts and ends.

Note

On Matlab Central there are several realizations for finding peaks, for example “peakfinder”, “peakseek”, or “peakdetect”. And “findpeaks” is also the name of a function in the Matlab ‘signal’ toolbox.

The parameter names are taken from the “findpeaks” function in ‘signal’, but the implementation utilizing regular expressions is unique and fast.

See Also

hampel

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
}
findpeaks(pSignal, npeaks=3, threshold=4, sortstr=TRUE)

## Not run: 
plot(pSignal, type="l", col="navy")
grid()
x <- findpeaks(pSignal, npeaks=3, threshold=4, sortstr=TRUE)
points(x[, 2], x[, 1], pch=20, col="maroon")
## End(Not run)

pracma documentation built on March 19, 2024, 3:05 a.m.