[R] add city and point in the map

[Alan Schussman]

YIHSU CHEN <yschen <at> jhu.edu> writes:

> 
> Dear Helpers:
> 
> I'm trying to use packages "maps" and "mapdata" (see blow) to display the
research resutls on map
> (Mid-Atlantic region).  In particular, I need to mark a number of points in
the map by giving their latitude
> and longitude information.  For instance, I would like to mark a point on
(long, lat) =(75.56027,

You can use library(mapproj) and the function mapproject() to do this.
mapproject converts longitude and latitude to x and y projections on a plot, as
in the following:

map('usa')
locations <- mapproject(longitude, latitude)
points(locations)

-Alan

--
-Alan Schussman / Graduate Associate
 University of Arizona Department of Sociology