ellipse: Get error ellipse coordinates for plotting

In IsoplotR: Statistical Toolbox for Radiometric Geochronology

Get error ellipse coordinates for plotting

Description

Constructs an error ellipse at a given confidence level from its centre and covariance matrix

Usage

ellipse(x, y, covmat, alpha = 0.05, n = 50)

Arguments

x	x-coordinate (scalar) for the centre of the ellipse
y	y-coordinate (scalar) for the centre of the ellipse
covmat	the [2x2] covariance matrix of the x-y coordinates
alpha	the probability cutoff for the error ellipses
n	the resolution (number of segments) of the error ellipses

Value

an [nx2] matrix of plot coordinates

Examples

x = 99; y = 101;
covmat <- matrix(c(1,0.9,0.9,1),nrow=2)
ell <- ellipse(x,y,covmat)
plot(c(90,110),c(90,110),type='l')
polygon(ell,col=rgb(0,1,0,0.5))
points(x,y,pch=21,bg='black')

IsoplotR documentation built on Oct. 19, 2024, 5:07 p.m.