localextrema: Finding Local Extrema and Zero-crossings of a Signal

In EPT: Ensemble Patch Transform, Visualization and Decomposition

Description

This function identifies local extrema and zero-crossings of a signal.

Usage

localextrema(y)

Arguments

y	a set of data or a signal.

Details

This function identifies local extrema and zero-crossings of a signal.

Value

minindex	matrix of time index at which local minima are attained. Each row specifies a starting and ending time index of a local minimum.
maxindex	matrix of time index at which local maxima are attained. Each row specifies a starting and ending time index of a local maximum.
nextreme	the number of extrema.
cross	matrix of time index of zero-crossings. Each row specifies a starting and ending time index of zero-crossings.
ncross	the number of zero-crossings.

See Also

eptransf, eptdecomp.

Examples

y <- c(0, 1, 2, 1, -1, 1:4, 5, 6, 0, -4, -6, -5:5, -2:2)
#y <- c(0, 0, 0, 1, -1, 1:4, 4, 4, 0, 0, 0, -5:5, -2:2, 2, 2)
#y <- c(0, 0, 0, 1, -1, 1:4, 4, 4, 0, 0, 0, -5:5, -2:2, 0, 0)

plot(y, type = "b"); abline(h = 0)
localextrema(y)

findextrema <- localextrema(y)
points(findextrema$maxindex, y[findextrema$maxindex], pch=16, col="red")
points(findextrema$minindex, y[findextrema$minindex], pch=16, col="blue")

Example output

$minindex
     [,1] [,2]
[1,]    5    5
[2,]   14   14
[3,]   26   26

$maxindex
     [,1] [,2]
[1,]    3    3
[2,]   11   11
[3,]   25   25

$nextreme
[1] 6

$cross
     [,1] [,2]
[1,]    1    1
[2,]    4    5
[3,]    5    6
[4,]   12   12
[5,]   20   20
[6,]   25   26
[7,]   28   28

$ncross
[1] 7

EPT documentation built on Jan. 5, 2022, 9:06 a.m.