Add Axis Labels to an Existing Map

Plot axis labels on an existing map. This is an advanced function, requiring coordination with mapPlot() and (possibly) also with mapGrid(), and so it is best avoided by novices, who may be satisfied with the defaults used by mapPlot().

mapAxis(
  side = 1:2,
  longitude = TRUE,
  latitude = TRUE,
  axisStyle = 1,
  tick = TRUE,
  line = NA,
  pos = NA,
  outer = FALSE,
  font = NA,
  lty = "solid",
  lwd = 1,
  lwd.ticks = lwd,
  col = NULL,
  col.ticks = NULL,
  hadj = NA,
  padj = NA,
  tcl = -0.3,
  cex.axis = 1,
  mgp = c(0, 0.5, 0),
  debug = getOption("oceDebug")
)

Arguments

side

the side at which labels are to be drawn. If not provided, sides 1 and 2 will be used (i.e. bottom and left-hand sides).

longitude

either a logical value or a numeric vector of longitudes. There are three possible cases: (1) If longitude=TRUE (the default) then ticks and nearby numbers will occur at the longitude grid established by the previous call to mapPlot(); (2) if longitude=FALSE then no longitude ticks or numbers are drawn; (3) if longitude is a vector of numerical values, then those ticks are placed at those values, and numbers are written beside them. Note that in cases 1 and 3, efforts are made to avoid overdrawing text, so some longitude values might get ticks but not numbers. To get ticks but not numbers, set cex.axis=0.

latitude

similar to longitude but for latitude.

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.

tick

parameter passed to axis().

line

parameter passed to axis().

pos

parameter passed to axis().

outer

parameter passed to axis().

font

axis font, passed to axis().

lty

axis line type, passed to axis().

lwd

axis line width, passed to axis()).

lwd.ticks

tick line width, passed to axis().

col

axis color, passed to axis().

col.ticks

axis tick color, passed to axis().

hadj

an argument that is transmitted to axis().

padj

an argument that is transmitted to axis().

tcl

axis-tick size (see par()).

cex.axis

axis-label expansion factor (see par()); set to 0 to prevent numbers from being placed in axes.

mgp

three-element numerical vector describing axis-label placement (see par()). It usually makes sense to set the first and third elements to zero.

debug

a flag that turns on debugging. Set to 1 to get a moderate amount of debugging information, or to 2 to get more.

See also

A map must first have been created with mapPlot().

Other functions related to maps: formatPosition(), lonlat2map(), lonlat2utm(), map2lonlat(), mapArrows(), mapContour(), mapCoordinateSystem(), mapDirectionField(), mapGrid(), mapImage(), mapLines(), mapLocator(), mapLongitudeLatitudeXY(), mapPlot(), mapPoints(), mapPolygon(), mapScalebar(), mapText(), mapTissot(), oceCRS(), oceProject(), shiftLongitude(), usrLonLat(), utm2lonlat()

Author

Dan Kelley

Examples

# \donttest{
library(oce)
data(coastlineWorld)
par(mar = c(2, 2, 1, 1))
lonlim <- c(-180, 180)
latlim <- c(70, 110)
# In mapPlot() call, note axes and grid args, to
# prevent over-plotting of defaults.  Some adjustments
# might be required to the mapGrid() arguments, to
# get agreement with the axis. This is why both
# mapGrid() and mapAxis() are best avoided; it is
# simpler to let mapPlot() handle these things.
mapPlot(coastlineWorld,
    projection = "+proj=stere +lat_0=90",
    longitudelim = lonlim, latitudelim = latlim,
    col = "tan", axes = FALSE, grid = FALSE
)
mapGrid(15, 15)
mapAxis(axisStyle = 5)

# }