- longitude
either a numeric vector of longitudes of points to be plotted, or
something (an oce object, a list, or a data frame) from which both
longitude and latitude may be inferred (in which case the latitude
argument is ignored). If longitude is missing, both it and
latitude are taken from the built-in coastlineWorld dataset.
- latitude
numeric vector of latitudes of points to be plotted (ignored
if the first argument contains both latitude and longitude).
- longitudelim
optional numeric vector of length two, indicating the
longitude limits of the plot. This value is used in the selection of
longitude lines that are shown (and possibly
labelled on the axes). In some cases, e.g. for polar views,
this can lead to odd results, with some expected longitude lines
being left out of the plot. Altering longitudelim can
often help in such cases, e.g. longitudelim=c(-180, 180) will
force the drawing of lines all around the globe.
- latitudelim
optional vector of length two, indicating
the latitude limits of the plot. This, together with longitudelim
(and, importantly, the geometry of the plot device) is used in the
selection of map scale.
- grid
either a number (or pair of numbers) indicating the spacing of
longitude and latitude lines, in degrees, or a logical value (or pair of
values) indicating whether to draw an auto-scaled grid, or whether to skip
the grid drawing. In the case of numerical values, NA can be used to
turn off the grid in longitude or latitude. Grids are set up based on
examination of the scale used in middle 10 percent of the plot area, and for
most projections this works quite well. If not, one may set
grid=FALSE and add a grid later with mapGrid().
- geographical
flag indicating the style of axes. With
geographical=0, the axes are conventional, with decimal degrees as
the unit, and negative signs indicating the southern and western
hemispheres. With geographical=1, the signs are dropped, with axis
values being in decreasing order within the southern and western
hemispheres. With geographical=2, the signs are dropped and the axes
are labelled with degrees, minutes and seconds, as appropriate, and
hemispheres are indicated with letters. With geographical=3, things
are the same as for geographical=2, but the hemisphere indication
is omitted. Finally, with geographical=4, unsigned numbers are used,
followed by letters N in the northern hemisphere, S in the southern,
E in the eastern, and W in the western.
- bg
color of the background (ignored).
- fill
is a deprecated argument; see oce-deprecated.
- border
color of coastlines and international borders (ignored unless
type="polygon".
- col
either the color for filling polygons (if type="polygon")
or the color of the points and line segments (if type="p",
type="l", or type="o"). If col=NULL then a default
will be set: no coastline filling for the type="polygon" case,
or black coastlines, for type="p", type="l", or
type="o".
- clip
logical value indicating whether to trim any coastline elements that lie wholly
outside the plot region. This can prevent e.g. a problem of filling the whole plot area of
an Arctic stereopolar view, because the projected trace for Antarctica lies outside all
other regions so the whole of the world ends up being "land". Setting clip=FALSE
disables this action, which may be of benefit in rare instances in the line connecting
two points on a coastline may cross the plot domain, even if those points are outside
that domain.
- type
indication of type; may be "polygon", for a filled polygon,
"p" for points, "l" for line segments, or "o" for points
overlain with line segments.
- axes
a logical value indicating whether to draw longitude and latitude
values in the lower and left margin, respectively. This may not work well
for some projections or scales. See also axisStyle, lonlabels
and latlabels, which offer more granular control of labelling.
- axisStyle
an integer specifying the style of labels for the numbers
on axes. The choices are:
1 for signed numbers without additional labels;
2 (the default) for unsigned numbers followed by letters indicating the hemisphere;
3 for signed numbers followed by a degree sign;
4 for unsigned numbers followed by a degree sign; and
5 for signed numbers followed by a degree sign and letters indicating the hemisphere.
- cex
character expansion factor for plot symbols,
used if type='p' or any other value that yields symbols.
- cex.axis
axis-label expansion factor (see par()).
- mgp
three-element numerical vector describing axis-label
placement, passed to mapAxis().
- drawBox
logical value indicating whether to draw a box around the plot.
This is helpful for many projections at sub-global scale.
- showHemi
logical value indicating whether to show the hemisphere in
axis tick labels.
- polarCircle
a number indicating the number of degrees of latitude
extending from the poles, within which zones are not drawn.
- lonlabels
An optional logical value or numeric vector that controls
the labelling along the horizontal axis. There are four possibilities:
(1) If lonlabels is TRUE (the default), then reasonable values are inferred
and axes are drawn with ticks and labels alongside those ticks;
(2) if lonlabels is FALSE, then ticks are drawn, but no labels;
(3) if lonlabels is NULL, then no axis ticks or labels are drawn; and
(4) if lonlabels is a vector of finite numerical values, then tick marks
are placed at those longitudes, and labels are put alongside them.
Note that R tries to avoid overwriting labels on axes, so the instructions
in case 4 might not be obeyed exactly.
See also latlabels, and note that setting axes=FALSE
ensures that no longitude or latitude axes will be drawn regardless
of the values of lonlabels and latlabels.
- latlabels
As lonlabels, but for latitude, on the left
plot axis.
- projection
optional indication of projection, in one of two
forms. First, it may be a character string in the "CRS" format that is
used by the sf package (and in much of modern computer-based
cartography). For example, projection="+proj=merc" specifies a
Mercator projection. The second format is the output from
sp::CRS() in the sp package, which is an object
with a slot named projarg that gets used as a projection string.
See “Details”.
- tissot
logical value indicating whether to use mapTissot()
to plot Tissot indicatrices, i.e. ellipses at grid intersection points, which
indicate map distortion.
- trim
logical value indicating whether to trim islands or lakes
containing only points that are off-scale of the current plot box. This
solves the problem of Antarctica overfilling the entire domain, for an
Arctic-centred stereographic projection. It is not a perfect solution,
though, because the line segment joining two off-scale points might
intersect the plotting box.
- debug
a flag that turns on debugging. Set to 1 to get a moderate
amount of debugging information, or to 2 to get more.
- ...
optional arguments passed to some plotting functions. This can
be useful in many ways, e.g. Example 5 shows how to use xlim etc to
reproduce a scale exactly between two plots.