time {diversitree}R Documentation

Support Functions for Time-varying Models

Description

Utility functions for working with time-dependent models.

Usage

constant.t(t, c)
linear.t(t, c, m)
exponential.t(t, y0, y1, r)
sigmoid.t(t, y0, y1, tmid, r)
stepf.t(t, y0, y1, tc)

make.pars.t(functions, cache=NULL, check.negative.const=TRUE,
            check.negative.var=TRUE)

Arguments

t

Time

c

Constant. For linear.t this is the value at t=0.

m

Slope

y0

y value at time 0 (exp.t) or very early times (limit as t tends to negative infinity in sigmoid.t)

y1

y value approached as t tends to negative infinity

r

Rate at which exponential decay occurs or sigmoid changes - higher values are steeper

tmid

Midpoint (inflection point) of sigmoid

tc

"Critical time" at which y changes from y0 to y1.

functions

A list of functions with t as their first argument.

cache

Internal use – please leave NULL.

check.negative.const, check.negative.var

Logicals, indicating if negative parameters should be checked for, for time-constant and time-varying parameters respectively.

Details

The linear function (linear.t) will go to zero wherever negative. This may not always be desired, but is often useful for models of rates.

Author(s)

Richard G. FitzJohn

[Package diversitree version 0.9-4 ]