Confidence Ellipses

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Description

Plot joint confidence ellipse for two parameters of secr model, or for a distribution of points.

Usage

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ellipse.secr(object, par = c("g0", "sigma"), alpha = 0.05,
    npts = 100, plot = TRUE, linkscale = TRUE, add = FALSE,
    col = palette(), ...)

ellipse.bvn(xy, alpha = 0.05, npts = 100, centroid = TRUE, add = FALSE, ...)

Arguments

object

secr object output from secr.fit

par

character vector of length two, the names of two ‘beta’ parameters

alpha

alpha level for confidence intervals

npts

number of points on perimeter of ellipse

plot

logical for whether ellipse should be plotted

linkscale

logical; if FALSE then coordinates will be backtransformed from the link scale

add

logical to add ellipse to an existing plot

col

vector of one or more plotting colours

...

arguments to pass to plot functions (or polygon() in the case of ellipse.bvn)

xy

2-column matrix of coordinates

centroid

logical; if TRUE the plotted ellipse is a confidence region for the centroid of points in xy

Details

ellipse.secr calculates coordinates of a confidence ellipse from the asymptotic variance-covariance matrix of the beta parameters (coefficients), and optionally plots it.

If linkscale == FALSE, the inverse of the appropriate link transformation is applied to the coordinates of the ellipse, causing it to deform.

If object is a list of secr models then one ellipse is constructed for each model. Colours are recycled as needed.

ellipse.bvn plots a bivariate normal confidence ellipse for the centroid of a 2-dimensional distribution of points (default centroid = TRUE), or a Jennrich and Turner (1969) elliptical home-range model.

Value

A list containing the x and y coordinates is returned invisibly from either function.

References

Jennrich, R. I. and Turner, F. B. (1969) Measurement of non-circular home range. Journal of Theoretical Biology, 22, 227–237.

Examples

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ellipse.secr(secrdemo.0)

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