Constructs and optionally plots a set of probability ellipses for a bivariate normal distribution with defined centre and covariance.
data.ellipse(cov, probs = 0.95, plot = TRUE, npoints = 100, ...) # S3 method for d.ellipse
summary(object, ...)
# S3 method for d.ellipse
print(x, ...)
Covariance and location object of class cov.dellipse
as returned by cov.dellipse()
A vector of probabilities at which ellipses will be constructed.
Logical specifying whether the ellipses constructed will additionally be plotted.
If TRUE
, the result is plotted using plot.d.ellipse()
Integer number of points for each quadrant of the ellipses returned.
Object of class d.ellipse
(for summary method).
Object of class d.ellipse
(for print method.
Arguments passed to other methods, particularly plot.d.ellipse
and, for print
,
format
and print.default
.
An object of class d.ellipse
, consisting of:
A named list of ellipsoids named for each probability in probs
.
Each is a \(4*npoints\times 2\) matrix suitable for passing direct to
polygon
.
Numeric vector of probabilities as supplied by probs
Covariance object of class cov.dellipse
as provided in cov
data.ellipse
constructs and returns one set of x, y coordinates for each value of
probs
, in a form that can be passed directly to polygon
.
Ellipses are constructed from the upper probs
quantile of the F distribution using
T = sqrt( 2 * (n - 1) * qf(probs, 2, n - 1)/(n - 2))
where n
is the number of pairs used in forming the covariance matrix.
If the number of points is missing or NA, Inf
is substituted.
Summary and print methods are provided. The summary method returns a list with the
same names as class d.ellipse
, each containing a default summary of the respective
member of the d.ellipse
object. The print method returns its argument invisibly.
ISO 13528:2005 Statistical methods for use in proficiency testing by interlaboratory comparisons. (2005) International organization for Standardizaton, Geneva
Jackson, J. E. (1956) Quality control methods for two related variables. Industrial Quality Control, Vol. 7, pp. 2-6
Jackson, J. E. (1959) Control Methods for Several Related Variables. Technometrics, Vol. 1, pp. 359-377
# NOT RUN {
data(chromium)
cov.Cr <- cov.dellipse(chromium)
dellipse.Cr <- data.ellipse(cov.Cr, plot=FALSE)
summary(dellipse.Cr)
# }
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