Classical (Metric) Multidimensional Scaling

Usage

cmdscale(d, k=2, eig=FALSE)

Arguments

d a distance structure such as that returned by dist or a full symmetric matrix containing the dissimilarities.
k the dimension of the space which the data are to be represented in.
eig indicates whether eigenvalues should be returned.

Description

Multidimensional scaling takes a set of dissimilarities and returns a set of points such that the distances between the points are approximately equal to the dissimilarities.

The functions isomds and sammon provide alternative ordination techniques.

Value

A list containing the following components.
points a matrix with k columns whose rows give the coordinates of the points chosen to represent the dissimilarities.
eig if requested,pthe eigenvalues computed during the scaling process.

Note

The S version of this function provides for computing an additional ``fiddle'' factor suggested by Togerson. R does not provide this option.

References

Seber, G. A. F. (1984). Multivariate Analysis. New York: Wiley.

Torgerson, W. S. (1958). Theory and Methods of Scaling. New York: Wiley.

See Also

dist, isomds, sammon.

Examples

data(eurodist)
loc <- cmdscale(eurodist)
x <- loc[,1]
y <- -loc[,2]
plot(x, y, type="n",
	xlab="", ylab="")
text(x, y, names(eurodist), cex=0.5)

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