schtrig function

Schmitt Trigger

Multisignal Schmitt trigger with levels.

schtrig(x, lvl, st = NULL)

Arguments

• x: input data, specified as a numeric vector or matrix. In case of a vector it represents a single signal; in case of a matrix each column is a signal.
• lvl: threshold levels against which x is compared, specified as a vector. If this is a scalar, the thresholds are symmetric around 0, i.e. c(-lvl, lvl).
• st: trigger state, specified as a vector of length ncol(x. The trigger state is returned in the output list and may be passed again to a subsequent call to schtrig. Default: NULL.

Returns

a list containing the following variables:

• v: vector or matrix of 0's and 1's, according to whether x is above or below lvl, or the value of x if indeterminate
• rng: ranges in which the output is high, so the indexes rng[1,i]:rng[2,i] point to the i-th segment of 1s in v. See clustersegment for a detailed explanation.
• st: trigger state, returned as a vector with a length of the number of columns in x.

Details

The trigger works compares each column in x to the levels in lvl, when the value is higher than max(lvl), the output v is high (i.e. 1); when the value is below min(lvl) the output is low (i.e. 0); and when the value is between the two levels the output retains its value.

Examples

t <- seq(0, 1, length.out = 100)
x <- sin(2 * pi * 2 * t) + sin(2 * pi * 5 * t) %*% matrix(c(0.8, 0.3), 1, 2)
lvl <- c(0.8, 0.25)
trig  <- schtrig (x, lvl)

op <- par(mfrow = c(2, 1))
plot(t, x[, 1], type = "l", xlab = "", ylab = "")
abline(h = lvl, col = "blue")
lines(t, trig$v[, 1], col = "red", lwd = 2)
plot(t, x[, 2], type = "l", xlab = "", ylab = "")
abline(h = lvl, col = "blue")
lines(t, trig$v[, 2], col = "red", lwd = 2)
par(op)

See Also

clustersegment

Author(s)

Juan Pablo Carbajal, carbajal@ifi.uzh.ch .

Conversion to R by Geert van Boxtel, G.J.M.vanBoxtel@gmail.com .