> I would like to know if there is any > possible way in which I could view those datapoints that are layered on top > of each other
You could use jitter() to add a little noise to the data. Of course that will slightly change the position of each point. If that is not an option you could possibly detect points with almost identical coordintes yourself and then change the color of the respective plotting symbol. cu Philipp -- Dr. Philipp Pagel Tel. +49-8161-71 2131 Dept. of Genome Oriented Bioinformatics Fax. +49-8161-71 2186 Technical University of Munich Science Center Weihenstephan 85350 Freising, Germany and Institute for Bioinformatics / MIPS Tel. +49-89-3187 3675 GSF - National Research Center Fax. +49-89-3187 3585 for Environment and Health Ingolstädter Landstrasse 1 85764 Neuherberg, Germany http://mips.gsf.de/staff/pagel ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.