localextrema {EPT}

Finding Local Extrema and Zero-crossings of a Signal

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")