A map

states <- map_data("state")
map <- qplot(long, lat, geom="polygon", fill=I("lightgrey"), colour=I("white"), group=group, data=states)

We don’t need the background, the grids or any x and y information (we should recognize a map without degree information).

Each plot has a theme - we can change the defaults by changing to a different theme, or by picking individual theme elements.

theme_grey is the default, but there are other themes, e.g. theme_bw, theme_lines, theme_minimal:

map + theme_bw()

map + theme_linedraw()

map + theme_minimal()