sitar (version 1.4.0)

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

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.

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)