The results of Self Organizing Maps (SOM) are plotted either in a table
with numbers (type="num") or with barplots (type="bar").
There is a limitation to at most 9 groups. A summary table is returned.
References
K. Varmuza and P. Filzmoser: Introduction to Multivariate Statistical
Analysis in Chemometrics. CRC Press, Boca Raton, FL, 2009.