paleoTS (version 0.3-1)

std.paleoTS: Standardize paleontological time series data

Description

This function standardizes a paleoTS object, converting the data to within-populations standard deviation units.

Usage

std.paleoTS(y, zero = "start")

Arguments

y

a paleontological time series

zero

if zero = "start", trait values are translated such that the initial starting value of the sequence is set to be zero. All other values are ignored.

Value

• the converted paleoTS object.

Details

The standardization expresses each sample mean as the deviation from the overall mean, divided by the pooled within-sample variance. 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 with different units.

References

Hunt, G. 2006. Fitting and comparing models of phyletic evolution: random walks and beyond. Paleobiology32:578--601.

See Also

ln.paleoTS

Examples

y<- sim.GRW(20, 0, 1, vp=10)
 ys<- std.paleoTS(y)
 fit3models(y)
 fit3models(ys)  # note Akaike weights do not change from standardization