sitar (version 1.5.0)

getPeakTrough: Identify peak or trough on curve

Description

Given vectors x and y, returns their values at the peak or trough of the smooth (e.g. cubic spline) curve y ~ x.

Usage

getPeakTrough(x, y = NULL, peak = TRUE, takeoff = FALSE, Dy = FALSE)
getPeak(x, y = NULL, peak = TRUE, takeoff = FALSE, Dy = FALSE)
getTrough(x, y = NULL, peak = FALSE, takeoff = FALSE, Dy = FALSE)
getTakeoff(x, y = NULL, peak = FALSE, takeoff = TRUE, Dy = FALSE)

Value

A length-2 vector containing the values of x and y at the peak or trough. If none are identified NA's are returned.

Arguments

x

vector.

y

vector.

peak

logical determining whether peak or trough is returned.

takeoff

logical determining whether, if peak is FALSE, the trough is takeoff.

Dy

logical if TRUE then y is differentiated first (default FALSE).

Author

Tim Cole

Details

Optionally the trough can be specified as takeoff, which is defined for a growth velocity curve as the lowest velocity before the pubertal peak, and if there is no peak then there is by definition no takeoff.

Examples

## create mean height velocity curve
data(heights)
m1 <- sitar(age, height, id, heights, 4)
## plot velocity curve
plot(m1, 'v')
## mark peak, trough and takeoff
xy <- plot_v(m1)
points(t(getPeak(xy)), pch=17)
points(t(getTrough(xy)), pch=25, col=2, bg=2)
points(t(getTakeoff(xy)), pch=25, col=3, bg=3)