I have an n x n symmetric matrix, with values equal to -1, 0, or 1. I plotted the matrix using image(), and levelplot(), giving different colors for -1, and 1 (0 implies no values, hence no color, or white).
However, I could not change the point style (using pch) for either of the two functions, or with heatmap and other options for that matter.
I trying to represent -1, and 1 with different colors, and different point styles (circle, and say, triangle). Something like shown here: http://www.ploscompbiol.org/article/fetchObject.action?uri=info:doi/10.1371/journal.pcbi.1002004.g007&representation=PNG_M
Thank you for your help.