| map {maps} | R Documentation |
Draw lines and polygons as specified by a map database.
map(database, regions) # simple form
map(database = "world", regions = ".", exact = FALSE, boundary = TRUE,
interior = TRUE, projection = "", parameters = NULL, orientation = NULL,
fill = FALSE, col = 1, plot = TRUE, add = FALSE, namesonly = FALSE,
xlim = NULL, ylim = NULL, wrap = FALSE, resolution = if(plot) 1 else 0,
type = "l", bg = par("bg"), mar = c(0, 0, par("mar")[3], 0.1),
border = 0.01, ...)
database |
character string naming a geographical database, or a list of
x, y, and names obtained from a previous call to
map.
The string choices include a world map,
three USA databases (usa, state,
county), and more (see the package index). The
location of the map databases may be overridden by setting the
R_MAP_DATA_DIR environment variable. See world
for further details.
|
regions |
character vector that names the polygons to draw.
Each database is composed of a collection of polygons, and each polygon has
a unique name.
When a region is composed of more than one polygon, the individual polygons
have the name of the region, followed by a colon and a qualifier,
as in michigan:north and michigan:south.
Each element of regions is matched
against the polygon names in the database and, according to
exact, a subset is selected for drawing.
The default selects all polygons in the database.
|
exact |
If TRUE, only exact matches with regions are
selected for drawing.
If FALSE, each element of regions is matched
as a regular expression
against the polygon names in the database and all matches are selected
for drawing.
|
boundary |
If FALSE, boundary segments are not drawn.
A boundary segment is a line segment of the map that bounds only
one of the polygons to be drawn.
This argument is ignored if fill is TRUE.
|
interior |
If FALSE, interior segments are not drawn.
An interior segment is a line segment of the map that bounds two
of the polygons to be drawn.
This argument is ignored if fill is TRUE.
|
projection |
character string that names a map projection to use.
See mapproject (in the mapproj library).
The default is to use a rectangular projection with the aspect ratio
chosen so that longitude and latitude scales are equivalent at the
center of the picture.
|
parameters |
numeric vector of parameters for use with the
projection argument.
This argument is optional only in the sense that certain
projections do not require additional parameters.
If a projection does require additional parameters, these
must be given in the parameters argument.
|
orientation |
a vector c(latitude, longitude, rotation) describing where
the map should be centered and a clockwise rotation (in degrees)
about this center.
|
fill |
logical flag that says whether to draw lines or fill areas.
If FALSE, the lines bounding each region will be drawn (but
only once, for interior lines).
If TRUE, each region will be filled using colors from the
col = argument, and bounding lines will not be drawn.
|
col |
vector of colors.
If fill is FALSE, the first color is used for plotting
all lines, and any other colors are ignored.
Otherwise, the colors are matched one-one with the polygons
that get selected by the region argument (and are reused
cyclically, if necessary).
A color of NA causes the corresponding region to be deleted
from the list of polygons to be drawn.
Polygon colors are assigned after polygons are deleted due to values
of the xlim and ylim arguments.
|
plot |
logical flag that specifies whether plotting
should be done.
If plot is TRUE the return value of map will
not be printed automatically .
|
add |
logical flag that specifies whether to add to the
current plot.
If FALSE, a new plot is begun, and a new coordinate
system is set up.
|
namesonly |
If TRUE, the return value will be a character vector of
the names of the selected polygons. See the Value section below.
|
xlim |
two element numeric
vector giving a range of longitudes, expressed
in degreees, to which drawing
should be restricted.
Longitude is measured in degrees east of Greenwich, so that, in particular,
locations in the USA have negative longitude.
If fill = TRUE, polygons selected by region must be entirely inside
the xlim range.
The default value of this argument spans the entire longitude range
of the database.
|
ylim |
two element
numeric vector giving a range of latitudes,
expressed in degrees, to which drawing
should be restricted.
Latitude is measured in degrees north of the
equator, so that, in particular,
locations in the USA have positive latitude.
If fill = TRUE, polygons selected by region must be entirely inside
the ylim range.
The default value of this argument spans the entire latitude range
of the database.
|
wrap |
If TRUE, lines that cross too far across the map (due to a strange projection) are omitted. |
resolution |
number that specifies the resolution with which
to draw the map.
Resolution 0 is the full resolution of the database.
Otherwise, just before polylines are plotted they are thinned:
roughly speaking, successive points on the polyline that are
within resolution device pixels of one another are collapsed
to a single point (see the Reference for further details).
|
type |
character string that controls drawing of the map.
Aside from the default type = "l", the value type = "n"
can be used
to set up the coordinate system and projection for a map that will
be added to in later calls.
|
bg |
background color. |
mar |
margins, as in par.
|
border |
scalar or vector of length 2 specifying the porportion of the plot to add to the defined or computed limits as borders. |
... |
Extra arguments passed to polygon or lines. |
If plot = TRUE, a plot is made where
the polygons selected from database, through the
regions, xlim, and ylim arguments, are outlined
(fill is FALSE) or filled (fill is TRUE)
with the colors in col.
The return value is a list with
x, y, range, and names components.
This object can be used as a database for successive calls
to map and functions.
If fill is FALSE, the x and y vectors are
the coordinates of successive polylines, separated by NAs. If
fill is TRUE, the x and y vectors have
coordinates of successive polygons, again separated by NAs.
Thus the return value can be handed directly to lines or
polygon, as appropriate.
When namesonly is TRUE, only the names component is returned.
After a call to map for which the projection argument was
specified there will be a global variable .Last.projection
containing information about the projection used.
This will be consulted in subsequent calls to map which use
projection = ''.
Richard A. Becker, and Allan R. Wilks, "Maps in S", AT&T Bell Laboratories Statistics Research Report [93.2], 1993. http://public.research.att.com/areas/stat/doc/93.2.ps
Richard A. Becker, and Allan R. Wilks, "Constructing a Geographical Database", AT&T Bell Laboratories Statistics Research Report [95.2], 1995. http://public.research.att.com/areas/stat/doc/95.2.ps
map.text, map.axes,
map.scale, map.grid (in the mapproj library)
map() # low resolution map of the world
map('usa') # national boundaries
map('county', 'new jersey') # county map of New Jersey
map('state', region = c('new york', 'new jersey', 'penn')) # map of three states
map("state", ".*dakota", border = 0) # map of the dakotas
map.axes() # show the effect of border = 0
if(require(mapproj))
map('state', proj = 'bonne', param = 45) # Bonne equal-area projection of states
# names of the San Juan islands in Washington state
map('county', 'washington,san', names = TRUE, plot = FALSE)
# national boundaries in one linetype, states in another
# (figure 5 in the reference)
map("state", interior = FALSE)
map("state", boundary = FALSE, lty = 2, add = TRUE)
# plot the ozone data on a base map
# (figure 4 in the reference)
data(ozone)
map("state", xlim = range(ozone$x), ylim = range(ozone$y))
text(ozone$x, ozone$y, ozone$median)
box()