Descriptive plots for categorical data

Catergorical or group-membership data ("factors" in R)  are often summarized in tables, the cells of which indicate absolute or relative frequencies of different combinations of the levels of the factors.  There are several approaches for visualizing the contents of a table.

attach(sumcr)
ReachHU.table <- table(Reach, HU)   # tabluate Reach and HU data
ReachHU.table

dotchart(ReachHU.table)
barplot(ReachHU.table)
mosaicplot(ReachHU.table, color=T)