tm_raster: Map layer: raster

In tmap: Thematic Maps

Map layer: raster

Description

Map layer that draws rasters. Supported map variable is: col (the color).

Usage

tm_raster(
  col = tm_vars(),
  col.scale = tm_scale(),
  col.legend = tm_legend(),
  col.chart = tm_chart_none(),
  col.free = NA,
  col_alpha = tm_const(),
  col_alpha.scale = tm_scale(),
  col_alpha.legend = tm_legend(),
  col_alpha.chart = tm_chart_none(),
  col_alpha.free = NA,
  zindex = NA,
  group = NA,
  group.control = "check",
  blend = "over",
  options = opt_tm_raster(),
  ...
)

opt_tm_raster(interpolate = FALSE)

Arguments

col, col.scale, col.legend, col.chart, col.free	Map variable that determines the color. See details. Unit: Color – a color name, hex string.
col_alpha, col_alpha.scale, col_alpha.legend, col_alpha.chart, col_alpha.free	Map variable that determines the color transparency. See details. Unit: Proportion – numeric 0-1 (0 = fully transparent, 1 = fully opaque).
zindex	Controls the stacking order of map layers. Should be set to a value above 400. By default, layers are stacked in call order, starting at 401. See details.
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).
blend	Compositing operator for layer blending. Default "over" applies no blending. See the "Layer blending" section for the supported values.
options	options passed on to the corresponding ⁠opt_<layer_function>⁠ function
...	to catch deprecated arguments from version < 4.0
interpolate	Should the raster image be interpolated? Currently only applicable in view mode (passed on to grid)

Details

The map variable arguments (e.g. col) can be specified with a data variable name (e.g., a spatial vector attribute or a raster layer of the object specified in tm_shape()), with a visual value (for col, a color is expected), or with a geometry-derived variable (see below). See vignette: Map variables.

Multiple values can be specified: in that case facets are created. These facets can be combined with other faceting data variables, specified with tm_facets(). See vignette: Facets.

• The ⁠*.scale⁠ arguments determine the used scale to map the data values to map variable values. These can be specified with one of the available ⁠tm_scale_*()⁠ functions. The default is specified by the tmap option (tm_options()) scales.var. See 'rvignette: Scales

• The ⁠*.legend⁠ arguments determine the used legend, specified with tm_legend(). The default legend and its settings are determined by the tmap options (tm_options()) legend. . See 'rvignette: Legends

• The ⁠*.chart⁠ arguments specify additional charts, specified with tm_chart_, e.g. tm_chart_histogram(). See 'rvignette: Charts

• The ⁠*.free⁠ arguments determine whether scales are applied freely across facets, or shared. A logical value is required. They can also be specified with a vector of three logical values; these determine whether scales are applied freely per facet dimension. This is only useful when facets are applied (see tm_facets()). There are maximally three facet dimensions: rows, columns, and pages. This only applies for a facet grid (tm_facets_grid()). For instance, col.free = c(TRUE, FALSE, FALSE) means that for the map variable col, each row of facets will have its own scale, and therefore its own legend. For facet wraps and stacks (tm_facets_wrap() and tm_facets_stack()) there is only one facet dimension, so the ⁠*.free⁠ argument requires only one logical value.

Currently, three geometry-derived variables are implemented:

• "AREA" (polygons only), which uses the feature area;

• "LENGTH" (lines only), which uses the feature length; and

• "MAP_COLORS", which assigns values so that adjacent features receive different values, making it particularly suitable for coloring neighbouring polygons.

Note that geometry-derived variables do not generate a legend automatically. If a legend is required, compute the corresponding variable explicitly, for example with sf::st_area(), sf::st_length(), or tmaptools::map_coloring(), and use the resulting values instead.

Map variable units

Every map variable maps data values to a specific output unit. Knowing the unit matters when supplying constant values via tm_const(), or output ranges via values.range / values.scale in the scale functions.

Variable	Output unit	Notes
fill, col, bgcol	color	name, hex, or palette string
fill_alpha, col_alpha, bgcol_alpha	proportion 0-1	0 = transparent, 1 = opaque
size (symbols, bubbles, squares, dots)	typographic lines	1 line approx. 1/6 inch; scaled by values.scale
size (circles)	meters	plain numeric or a units object
size (text, labels)	multiplier	1 = 12 pt (plot) / 12 px (view)
lwd	lwd	base R units; 1 lwd approx. 0.75 pt at 96 dpi
lty	--	integer 1-6 or name ("solid", "dashed", ...)
shape	--	integer pch 1-25 or single character
angle	degrees	0-360, clockwise from north
fontface	--	"plain", "bold", "italic", "bold.italic"

Symbol size (size in tm_symbols, tm_bubbles, tm_squares, tm_dots)

"Lines" is a typographic unit: one line is approximately 1/6 inch (the default base line-height in R graphics). The global multiplier tmap_options(values.scale = list(size.bubbles = 1.5)) scales all symbol sizes without changing the data mapping.

Circle size (size in tm_circles)

The value is a geographic radius in meters. A plain numeric vector is interpreted as meters; a units object (from the units package) is automatically converted, so units::as_units(1, "mi") gives a 1-mile radius. Because the radius is geographic, circles scale with zoom in interactive (view) mode – unlike bubble symbols which keep a fixed screen size.

Text size (size in tm_text, tm_labels)

The value is a multiplier of the base font size. size = 1 renders at 12 pt in plot mode (R's default par("ps")) and at 12 px in view mode (gp$cex * 12 px, see tmapLeafletDataPlot.tm_data_text); the two modes are consistent by design.

Layer blending (blend)

Blend modes control how a layer's pixels are combined with the pixels beneath it. For each pixel, let S be the source (top layer) RGB value and D be the destination (bottom layer) RGB value, both normalised to [0, 1].

blend	Formula	Use case
"over"	S \cdot \alpha + D \cdot (1 - \alpha)	Standard alpha compositing (default)
"multiply"	S \times D	Hillshading over color raster; both layers darken each other
"screen"	1 - (1 - S)(1 - D)	Inverse of multiply; brightens
"overlay"	multiply if D < 0.5, screen if D \geq 0.5	Boosts contrast; preserves midtones
"darken"	\min(S, D)	Keeps the darker of the two layers per channel
"lighten"	\max(S, D)	Keeps the lighter of the two layers per channel

Requires R >= 4.2 and a compatible graphics device (e.g. png(type = "cairo"), svg()). In view mode, blending is applied via CSS mix-blend-mode. See grid::groupGrob() for the full list of supported operators.

zindex and pane names

In view mode, each layer is rendered in a Leaflet pane named "tmap{zindex}" (e.g., "tmap401", "tmap402"), with base tile layers placed in the standard "tile" pane.

Examples

## Not run: 
# load land data
data(land, World)

tm_shape(land) +
	tm_raster("cover")

tm_shape(land) +
	tm_raster("elevation", col.scale = tm_scale_continuous(values = terrain.colors(9))) +
	tm_shape(World) +
	tm_borders()

## End(Not run)

tmap documentation built on June 26, 2026, 5:08 p.m.