heplot.candisc {candisc}R Documentation

Canonical Discriminant HE plots

Description

These functions plot ellipses (or ellipsoids in 3D) in canonical discriminant space representing the hypothesis and error sums-of-squares-and-products matrices for terms in a multivariate linear model. They provide a low-rank 2D (or 3D) view of the effects for that term in the space of maximum discrimination.

Usage

## S3 method for class 'candisc':
heplot(mod, which = 1:2, scale, asp = 1, var.col = "blue", 
    var.lwd = par("lwd"), prefix = "Can", terms = mod$term, ...)

## S3 method for class 'candisc':
heplot3d(mod, which = 1:3, scale, var.col = "blue", 
    prefix = "Can", terms = mod$term, 
    ...) 

Arguments

mod A candisc object for one term in a mlm
which A numeric vector containing the indices of the canonical dimensions to plot.
scale Scale factor for the variable vectors in canonical space. If not specified, the function calculates one to make the variable vectors approximately fill the plot window.
asp Aspect ratio for the horizontal and vertical dimensions. The default, asp=1 ensures equal units, so that angles and lengths of variable vectors are interpretable. As well, the standardized canonical scores are uncorrelated, so the Error ellipse (ellipsoid) should plot as a circle (sphere) in canonical space.
var.col Color for variable vectors and labels
var.lwd Line width for variable vectors
prefix Prefix for labels of canonical dimensions.
terms Terms from the original mlm whose H ellipses are to be plotted in canonical space. The default is the one term for which the canonical scores were computed. If terms=TRUE, all terms are plotted.
... Arguments to be passed down

Details

The generalized canonical discriminant analysis for on term in a mlm is based on the eigenvalues, lambda_i, and eigenvectors, V, of the H and E matrices for that term. This produces uncorrelated canonical scores which give the maximum univariate F statistics. The canonical HE plot is then just the HE plot of the canonical scores for the given term.

Value

No useful value; used for the side-effect of producing a canonical HE plot.

Author(s)

Michael Friendly and John Fox

References

Friendly, M. (2006). Data Ellipses, HE Plots and Reduced-Rank Displays for Multivariate Linear Models: SAS Software and Examples Journal of Statistical Software, 17(6), 1-42. http://www.jstatsoft.org/v17/i06/

Friendly, M. (2007). HE plots for Multivariate General Linear Models. Journal of Computational and Graphical Statistics, 16 (2), 421-444. http://www.math.yorku.ca/SCS/Papers/heplots.pdf

See Also

candisc, candiscList, heplot, heplot3d

Examples

grass.mod <- lm(cbind(N1,N9,N27,N81,N243) ~ Block + Species, data=Grass)

grass.can1 <-candisc(grass.mod, term="Species")
grass.canL <-candiscList(grass.mod)

heplot(grass.can1, scale=6)
heplot(grass.can1, scale=6, terms=TRUE)
heplot(grass.canL, terms=TRUE, ask=FALSE)

# NB: aspect3d not set for equal scaling in this plot 
heplot3d(grass.can1)


[Package candisc version 0.5-9 Index]