R/veganCovEllipse.R

In vegan: Community Ecology Package

`veganCovEllipse` <-
    function(cov, center = c(0,0), scale = 1, npoints = 100)
{
    ## Basically taken from the 'car' package: The Cirlce
    theta <- (0:npoints) * 2 * pi/npoints
    Circle <- cbind(cos(theta), sin(theta))
    ## scale, center and cov must be calculated separately
    Q <- chol(cov, pivot = TRUE)
    ## pivot takes care of cases when points are on a line
    o <- attr(Q, "pivot")
    t(center + scale * t(Circle %*% Q[,o]))
}