ConcEllipse function

Concentration ellipse for a se of two-dimensional points

The function calculates a non-parametric concentration ellipse for a set of two-dimensional points.

ConcEllipse(data, confidence=1, npoints=100)

Arguments

• data: The set of two-dimensional points
• confidence: Percentage of points to be included in the ellipse
• npoints: Number of points to draw the eelipse contour. The hier the number of points the smouther is the ellipse.

Details

The procedre uses the Mahalanobis distances to determine the points that will be used for the calculations.

Returns

A list with the following fields - data: Data Used for the calculations

• confidence: The confidence level used

• ellipse: The points on the ellipse contour to be plotted

• center: The center of the points

References

Meulman, J. J., & Heiser, W. J. (1983). The display of bootstrap solutions in multidimensional scaling. Murray Hill, NJ: Bell Laboratories.

Linting, M., Meulman, J. J., Groenen, P. J., & Van der Kooij, A. J. (2007). Stability of nonlinear principal components analysis: An empirical study using the balanced bootstrap. Psychological Methods, 12(3), 359.

Author(s)

Jose Luis Vicente Villardon

Examples

data(iris)
dat=as.matrix(iris[1:50,1:2])
plot(iris[,1], iris[,2],col=iris[,5], asp=1)
E=ConcEllipse(dat, 0.95)
plot(E)