geiger (version 1.0-91)

area.between.curves: Area between two curves

Description

Finds the area between two curves (f1 and f2) for a given range on the x-axis. One use for this function is to calculate the MDI statistic from Harmon et al. 2003

Usage

area.between.curves(x, f1, f2, xrange = c(0,1))

Arguments

x

Vector of values for the x axis

f1

Y values for curve 1

f2

Y values for curve 2

xrange

Range of x values over which area is calculated

Value

• Area between f1 and f2 between 0 and cutoff

Details

Area is calculated between the two curves f1 and f2 for x values in the given range. If f2 is greater than f1, areas are positive; otherwise, areas are negative

References

Harmon, L. J., J. A. Schulte, J. B. Losos, and A. Larson. 2003. Tempo and mode of evolutionary radiation in iguanian lizards. Science 301: 961-964.

Examples

data(geospiza)
attach(geospiza)

gg<-dtt.full(geospiza.tree, geospiza.data)

# Full area, as in dtt.full function
area.between.curves(gg$times, apply(gg$dtt.sims,1,mean), gg$dtt.data)

# Area for first 2/3, as in Harmon et al. 2003
area.between.curves(gg$times, apply(gg$dtt.sims,1,median), gg$dtt.data, xrange=c(0, 2/3))

# You could also use the mean
area.between.curves(gg$times, apply(gg$dtt.sims,1,mean), gg$dtt.data, xrange=c(0, 2/3))