plot-coastline-method: Plot a coastline Object
In oce: Analysis of Oceanographic Data

plot,coastline-method

R Documentation

Plot a coastline Object

Description

This function plots a coastline. An attempt is made to fill the space of the plot, and this is done by limiting either the longitude range or the latitude range, as appropriate, by modifying the eastern or northern limit, as appropriate.

Usage

## S4 method for signature 'coastline'
plot(
  x,
  xlab = "",
  ylab = "",
  showHemi = TRUE,
  asp,
  clongitude,
  clatitude,
  span,
  lonlabels = TRUE,
  latlabels = TRUE,
  projection = NULL,
  expand = 1,
  mgp = getOption("oceMgp"),
  mar = c(mgp[1] + 1, mgp[1] + 1, 1, 1),
  bg,
  fill,
  type = "polygon",
  border = NULL,
  col = NULL,
  axes = TRUE,
  cex.axis = par("cex.axis"),
  add = FALSE,
  inset = FALSE,
  geographical = 0,
  longitudelim,
  latitudelim,
  debug = getOption("oceDebug"),
  ...
)

Arguments

`x`	a coastline object.
`xlab`	label for x axis
`ylab`	label for y axis
`showHemi`	logical indicating whether to show the hemisphere in axis tick labels.
`asp`	Aspect ratio for plot. The default is for `⁠plot,coastline-method⁠` to set the aspect ratio to give natural latitude-longitude scaling somewhere near the centre latitude on the plot. Often, it makes sense to set `asp` yourself, e.g. to get correct shapes at 45N, use `asp=1/cos(45*pi/180)`. Note that the land mass is not symmetric about the equator, so to get good world views you should set `asp=1` or set `ylim` to be symmetric about zero. Any given value of `asp` is ignored, if `clongitude` and `clatitude` are given (or if the latter two are inferred from `projection`.
`clongitude`, `clatitude`	optional center latitude of map, in decimal degrees. If both `clongitude` and `clatitude` are provided, or alternatively if they can be inferred from substrings `+lon_0` and `+lat_0` in `projection`, then any provided value of `asp` is ignored, and instead the plot aspect ratio is computed based on the center latitude. If `clongitude` and `clatitude` are known, then `span` must also be provided, and in this case, it is not permitted to also specify `longitudelim` and `latitudelim`.
`span`	optional suggested diagonal span of the plot, in kilometers. The plotted span is usually close to the suggestion, although the details depend on the plot aspect ratio and other factors, so some adjustment may be required to fine-tune a plot. A value for `span` must be supplied, if `clongitude` and `clatitude` are supplied (or inferred from `projection`).
`lonlabels`, `latlabels`	optional vectors of longitude and latitude to label on the sides of plot, passed to `mapPlot()` to control axis labelling, for plots done with map projections (i.e. for cases in which `projection` is not `NULL`).
`projection`	optional map projection to use (see the `mapPlot()` argument of the same name). If set to `FALSE` then no projection is used, and the data are plotted in a cartesion frame, with aspect ratio set to reduce distortion near the middle of the plot. This option is useful if the coastline produces spurious horizontal lines owing to islands crossing the plot edges (a problem that plagues map projections). If `projection` is not set, a Mercator projection is used for latitudes below about 70 degrees, as if `projection="+proj=merc"` had been supplied, or a Stereopolar one is used as if `projection="+proj=stere"`. Otherwise, `projection` must be a character string identifying a projection accepted by `mapPlot()`.
`expand`	numerical factor for the expansion of plot limits, showing area outside the plot, e.g. if showing a ship track as a coastline, and then an actual coastline to show the ocean boundary. The value of `expand` is ignored if either `xlim` or `ylim` is given.
`mgp`	3-element numerical vector to use for `par("mgp")`, and also for `par(mar)`, computed from this. The default is tighter than the R default, in order to use more space for the data and less for the axes.
`mar`	value to be used with `par("mar")`.
`bg`	optional color to be used for the background of the map. This comes in handy for drawing insets (see “details”).
`fill`	a legacy parameter that will be permitted only temporarily; see “History”.
`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. See `color` for a note on how the the value of `type` alters the meaning of the `color` argument.
`border`	color used to indicate land (if `type="polygon"`) or the coastline and international borders (if `type="l"`).
`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"`).
`axes`	boolean, set to `TRUE` to plot axes.
`cex.axis`	value for axis font size factor.
`add`	boolean, set to `TRUE` to draw the coastline on an existing plot. Note that this retains the aspect ratio of that existing plot, so it is important to set that correctly, e.g. with `asp=1/cos(lat * pi / 180)`, where `clat` is the central latitude of the plot.
`inset`	set to `TRUE` for use within `plotInset()`. The effect is to prevent the present function from adjusting margins, which is necessary because margin adjustment is the basis for the method used by `plotInset()`.
`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.
`longitudelim`	this and `latitudelim` provide a second way to suggest plot ranges. Note that these may not be supplied if `clongitude`, `clatitude` and `span` are given.
`latitudelim`	see `longitudelim`.
`debug`	set to `TRUE` to get debugging information during processing.
`...`	optional arguments passed to plotting functions. For example, set `yaxp=c(-90,90,4)` for a plot extending from pole to pole.

Details

If longitudelim, latitudelim and projection are all given, then these arguments are passed to mapPlot() to produce the plot. (The call uses bg for col, and uses col, fill and border directly.) If the results need further customization, users should use mapPlot() directly.

If projection is provided without longitudelim or latitudelim, then mapPlot() is still called, but longitudelim and latitudelim are computed from clongitude, clatitude and span.

If projection is not provided, much simpler plots are produced. These are Cartesian, with aspect ratio set to minimize shape distortion at the central latitude. Although these are crude, they have the benefit of always working, which cannot be said of true map projections, which can be problematic in various ways owing to difficulties in inverting projection calculations.

To get an inset map inside another map, draw the first map, do par(new=TRUE), and then call plot,coastline-method() with a value of mar that moves the inset plot to a desired location on the existing plot, and with bg="white".

Value

None.

History

Until February, 2016, ⁠plot,coastline-method⁠ relied on a now-defunct argument fill to control colors; col is to be used now, instead.

Author(s)

Dan Kelley

Examples


library(oce)
par(mar = c(2, 2, 1, 1))
data(coastlineWorld)
plot(coastlineWorld)
plot(coastlineWorld, clongitude = -63.6, clatitude = 44.6, span = 1000)

# Canada in Lambert projection
plot(coastlineWorld,
    clongitude = -95, clatitude = 65, span = 5500,
    grid = 10, projection = "+proj=laea +lon_0=-100 +lat_0=55"
)

oce documentation built on Sept. 11, 2024, 7:09 p.m.