Find Peaks
Find peaks (maxima) in a time series.
findpeaks(x, nups = 1, ndowns = nups, zero = "0", peakpat = NULL,
minpeakheight = -Inf, minpeakdistance = 1,
threshold = 0, npeaks = 0, sortstr = FALSE)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, the parameters
|
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 |
This function is quite general as it relies on regular patterns to determine where a peak is located, from beginning to end.
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.
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.
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)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.