[R] mca-graphics: all elements overlapping in the help-example for multiple correspondence analysis

Prof Brian Ripley ripley at stats.ox.ac.uk
Wed Jan 31 10:19:21 CET 2007

On Wed, 31 Jan 2007, Michael Reinecke wrote:

> Dear all,
> I tried out the example in the help document for mca (the multiple correspondence analysis of the MASS package):
> farms.mca <- mca(farms, abbrev=TRUE)
> farms.mca
> plot(farms.mca)
> But the graphic that I get seems unfeasible to me: I cannot recognize 
> the numbers (printed in black) because they are all overlapping and 
> concealing each other. I don ´t dare using my own data, which consist of 
> several hundred cases - I guess I won ´t see anything.
> How can I solve this? Thank you for any idea!

Some levels do overplot, as they are identical (this is an unusual 
example).  But as you see in the book, not many, and you can 
adjust pointsize of your device or 'cex' to mitigate the problem.

Plotting the rows is optional: see the help page.  I would not recommend 
plotting rows for several hundred cases.

Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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