ellipse3d.axes {heplots} | R Documentation |
A function to draw the major axes of a 3D ellipsoid from a correlation, covariance or sums of squares and cross products matrix.
ellipse3d.axes(x, centre = c(0, 0, 0), scale = c(1, 1, 1), level = 0.95, t = sqrt(qchisq(level, 3)), which = 1:3, labels = TRUE, label.ends=c(2,4,6), ...)
x |
A square positive definite matrix at least 3x3 in size. It will be treated as the correlation or covariance of a multivariate normal distribution. |
centre |
The center of the ellipse |
scale |
If x is a correlation matrix, then the standard deviations of each parameter can be given in the scale parameter.
This defaults to c(1, 1, 1) , so no rescaling will be done. |
level |
The confidence level of a simulataneous confidence region. The default is 0.95, for a 95% region. This is used to control the size of the ellipsoid. |
t |
The size of the ellipsoid may also be controlled by specifying the value of a t-statistic on its boundary. |
which |
This parameter selects which variables from the object will be plotted. The default is the first 3. |
labels |
Either a logical value, a character string, or a character vector of length 3.
If TRUE , the default, the axes are labeled PC1, PC2, PC3.
If a single character string, the digits 1, 2, 3 are pasted on the end. |
label.ends |
A vector of lengeth 3 indicating which ends of the axes should
be labeled, corresponding to a selection of rows of the 6 x 3 matrix of axes
end points. Default: c(2,4,6) . |
... |
Other arguments passed to segments3d and text3d . |
Returns a 6 x 3 matrix containing the end points of the three axis lines in pairs by rows.
Michael Friendly
data(iris) iris3 <- iris[,1:3] cov <- cov(iris3) mu <- mean(iris3) col <-c("blue", "green", "red")[iris$Species] library(rgl) plot3d(iris3, type="s", size=0.4, col=col, cex=2, box=FALSE, aspect="iso") plot3d( ellipse3d(cov, centre=mu, level=0.68), col="gray", alpha=0.2, add = TRUE) axes <- ellipse3d.axes(cov, centre=mu, level=0.68)