tm_grid: Coordinate grid / graticule lines

In tmap: Thematic Maps

Coordinate grid / graticule lines

Description

Draws horizontal and vertical lines according to a coordinate reference system (CRS). tm_grid() uses the CRS of the (master) shape object, and tm_graticules() uses latitude and longitude coordinates (EPSG 4326). It creates a tmap-element that draws coordinate grid lines. It serves as a layer that can be drawn anywhere between other layers.

Usage

tm_graticules(
  x = NA,
  y = NA,
  n.x = NA,
  n.y = NA,
  crs = 4326,
  labels.format = list(suffix = intToUtf8(176)),
  labels.cardinal = TRUE,
  ...
)

tm_grid(
  x = NA,
  y = NA,
  n.x = NA,
  n.y = NA,
  crs = NA,
  col = NA,
  lwd = 1,
  alpha = NA,
  labels.show = TRUE,
  labels.pos = c("left", "bottom"),
  labels.size = 0.6,
  labels.col = NA,
  labels.rot = c(0, 0),
  labels.format = list(big.mark = ","),
  labels.cardinal = FALSE,
  labels.margin.x = 0,
  labels.margin.y = 0,
  labels.space.x = NA,
  labels.space.y = NA,
  labels.inside_frame = FALSE,
  ticks = labels.show & !labels.inside_frame,
  lines = TRUE,
  ndiscr = 100,
  zindex = NA,
  group = NA,
  group.control = "none",
  ...
)

Arguments

x	X coordinates for vertical grid lines. If NA, it is specified with a pretty scale and n.x.
y	Y coordinates for horizontal grid lines. If NA, it is specified with a pretty scale and n.y.
n.x	Preferred number of grid lines for the x axis. For the labels, a pretty() sequence is used, so the number of actual labels may be different than n.x.
n.y	Preferred number of grid lines for the y axis. For the labels, a pretty() sequence is used, so the number of actual labels may be different than n.y.
crs	Projection character. If specified, the grid lines are projected accordingly. Many world maps are projected, but still have latitude longitude (EPSG 4326) grid lines.
labels.format	List of formatting options for the grid labels. Parameters are: fun Function to specify the labels. It should take a numeric vector, and should return a character vector of the same size. By default it is not specified. If specified, the list items scientific, format, and digits (see below) are not used. scientific Should the labels be formatted scientifically? If so, square brackets are used, and the format of the numbers is "g". Otherwise, format="f", and text.separator, text.less.than, and text.or.more are used. Also, the numbers are automatically rounded to millions or billions if applicable. format By default, "f", i.e. the standard notation xxx.xxx, is used. If scientific=TRUE then "g", which means that numbers are formatted scientifically, i.e. n.dddE+nn if needed to save space. digits Number of digits after the decimal point if format="f", and the number of significant digits otherwise. ... Other arguments passed on to formatC()
labels.cardinal	Add the four cardinal directions (N, E, S, W) to the labels, instead of using negative coordinates for west and south (so it assumes that the coordinates are positive in the north-east direction).
...	Used to catch deprecated arguments from tmap v3.
col	Color of the grid lines.
lwd	Line width of the grid lines
alpha	Alpha transparency of the grid lines. Number between 0 and 1. By default, the alpha transparency of col is taken.
labels.show	Show tick labels. Either one value for both x and y axis, or a vector two: the first for x and latter for y.
labels.pos	position of the labels. Vector of two: the horizontal ("left" or "right") and the vertical ("top" or "bottom") position.
labels.size	Font size of the tick labels
labels.col	Font color of the tick labels
labels.rot	Rotation angles of the labels. Vector of two values: the first is the rotation angle (in degrees) of the tick labels on the x axis and the second is the rotation angle of the tick labels on the y axis. Only 0, 90, 180, and 270 are valid values.
labels.margin.x	Margin between tick labels of x axis and the frame. Note that when labels.inside_frame = FALSE and ticks = TRUE, the ticks will be adjusted accordingly.
labels.margin.y	Margin between tick labels of y axis and the frame. Note that when labels.inside_frame = FALSE and ticks = TRUE, the ticks will be adjusted accordingly.
labels.space.x	Space that is used for the labels and ticks for the x-axis when labels.inside_frame = FALSE. By default, it is determined automatically using the widths and heights of the tick labels. The unit of this parameter is text line height.
labels.space.y	Space that is used for the labels and ticks for the y-axis when labels.inside_frame = FALSE. By default, it is determined automatically using the widths and heights of the tick labels. The unit of this parameter is text line height.
labels.inside_frame	Show labels inside the frame? By default FALSE.
ticks	If labels.inside_frame = FALSE, should ticks can be drawn between the labels and the frame? Either one value for both x and y axis, or a vector two: the first for x and latter for y.
lines	If labels.inside_frame = FALSE, should grid lines can be drawn?
ndiscr	Number of points to discretize a parallel or meridian (only applicable for curved grid lines)
zindex	zindex of the pane in view mode. By default, it is set to the layer number plus 400. By default, the tmap layers will therefore be placed in the custom panes "tmap401", "tmap402", etc., except for the base tile layers, which are placed in the standard "tile". This parameter determines both the name of the pane and the z-index, which determines the pane order from bottom to top. For instance, if zindex is set to 500, the pane will be named "tmap500".
group	Name of the group to which this layer belongs. This is only relevant in view mode, where layer groups can be switched (see group.control)
group.control	In view mode, the group control determines how layer groups can be switched on and off. Options: "radio" for radio buttons (meaning only one group can be shown), "check" for check boxes (so multiple groups can be shown), and "none" for no control (the group cannot be (de)selected).

Examples

## Not run: 
current.mode <- tmap_mode("plot")

tm_shape(NLD_muni) +
	tm_polygons() +
	tm_grid()

tm_shape(NLD_muni) +
	tm_polygons() +
	tm_grid(crs = 4326)

tm_shape(NLD_muni) +
	tm_polygons() +
	tm_grid(crs = 3035, labels.inside.frame = TRUE)

tm_shape(World) +
	tm_polygons() +
	tm_facets(by = "continent") +
	tm_grid(labels.inside.frame = TRUE)

tm_shape(NLD_muni) +
	tm_polygons() +
	tm_graticules()

tm_shape(NLD_muni) +
	tm_polygons() +
	tm_graticules(labels.pos = c("right", "top"))


data(NLD_muni, World)

tmap_arrange(
	qtm(NLD_muni) + tm_grid(),
	qtm(NLD_muni) + tm_graticules()
)

qtm(World, shape.crs = "+proj=robin", style = "natural") +
	tm_graticules(ticks = FALSE) +
	tm_layout(frame=FALSE)

tmap_mode(current.mode)

## End(Not run)

tmap documentation built on April 4, 2025, 2:05 a.m.