Point coordinates for a 2-D ellipse.
Calculates coordinates of points for plotting a 2-dimensional ellipse based on user-defined parameters. Can be used for exploratory data analysis to produce ellipses at a given niche region size (e.g., α = 95\%).
ellipse(mu, V, alpha = 0.95, n = 100)
mu |
centre of ellipse. A vector of length 2. |
V |
scale of ellipse. A 2x2 matrix. See Details. |
alpha |
niche region size. See Details. |
n |
number of points to return for plotting. |
This function provides the coordinates needed to plot a 2-dimensional ellipse
based on user-defined parameters, such that X = c(x,y) satisfies the equation
(X-μ)' V^{-1} (X-μ) = C,
where C=\code{qchisq(alpha, df = 2)}.
Returns a matrix of coordinates cbind(x,y) to plot a 2-dimensional ellipse.
mu <- rnorm(2) V <- crossprod(matrix(rnorm(4), 2, 2)) ell.pts <- ellipse(mu = mu, V = V, alpha = .9, n = 100) plot(ell.pts, col = rainbow(110)[1:100], type = "o") points(mu[1], mu[2], pch = "+")
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