paleoTS (version 0.6.2)

std.paleoTS: Convert time-series to standard deviation units

Description

Convert time-series to standard deviation units

Usage

std.paleoTS(y, center = c("mean", "start"))

Value

the converted paleoTS object

Arguments

y

a paleoTS object

center

optional translation of time-series according to "mean" or "start"; see Details

Details

The standardization expresses each sample mean as the deviation from the overall mean, divided by the pooled within-sample standard deviation. Sample variances are also divided by the pooled sample variance.

Essentially, this converts paleontological time-series data into standard deviation units, similar to the computation of evolutionary rates in haldanes. This operation does not change the relative fit of models, but it does facilitate the comparison of parameter estimates across time-series of traits measured in different units.

If argument center = "start" the time-series is translated such that the trait mean of the first sample is zero.

Examples

x <- sim.Stasis(ns = 8, theta = 1, omega = 4, vp = 2)
xs <- std.paleoTS(x, center = "start")
plot(x, ylim = range(c(x$mm, xs$mm)))
plot(xs, col = "red", add = TRUE)
legend(x = "topright", c("unstandardized", "standardized"), lty=1, col=c("black", "red"), cex=0.7)