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Map layer: lines

Source: R/tm_layers_lines.R
tm_lines.Rd

Map layer that draws lines. Supported visual variables are: col (the color), lwd (line width), lty (line type), and col_alpha (color alpha transparency).

Usage

tm_lines(
  col = tm_const(),
  col.scale = tm_scale(),
  col.legend = tm_legend(),
  col.chart = tm_chart_none(),
  col.free = NA,
  lwd = tm_const(),
  lwd.scale = tm_scale(),
  lwd.legend = tm_legend(),
  lwd.chart = tm_chart_none(),
  lwd.free = NA,
  lty = tm_const(),
  lty.scale = tm_scale(),
  lty.legend = tm_legend(),
  lty.chart = tm_chart_none(),
  lty.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,
  linejoin = "round",
  lineend = "round",
  plot.order = tm_plot_order("lwd", reverse = TRUE, na.order = "bottom"),
  zindex = NA,
  group = NA,
  group.control = "check",
  popup.vars = NA,
  popup.format = tm_label_format(),
  hover = NA,
  id = "",
  options = opt_tm_lines(),
  ...
)

opt_tm_lines(lines.only = "ifany", hitbox = "auto")

Arguments

col, col.scale, col.legend, col.chart, col.free

Visual variable that determines the color. See details.

lwd, lwd.scale, lwd.legend, lwd.chart, lwd.free

Visual variable that determines the line width. See details.

lty, lty.scale, lty.legend, lty.chart, lty.free

Visual variable that determines the line type. See details.

col_alpha, col_alpha.scale, col_alpha.legend, col_alpha.chart, col_alpha.free

Visual variable that determines the color transparency. See details.

linejoin, lineend

line join and line end. See gpar() for details.

plot.order

Specification in which order the spatial features are drawn. See tm_plot_order() for details.

zindex

Map layers are drawn on top of each other. The zindex numbers (one for each map layer) determines the stacking order. By default the map layers are drawn in the order they are called.

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).

popup.vars

names of data variables that are shown in the popups in "view" mode. Set popup.vars to TRUE to show all variables in the shape object. Set popup.vars to FALSE to disable popups. Set popup.vars to a character vector of variable names to those those variables in the popups. The default (NA) depends on whether visual variables (e.g.fill) are used. If so, only those are shown. If not all variables in the shape object are shown.

popup.format

list of formatting options for the popup values. Output of tm_label_format(). Only applicable for numeric data variables. If one list of formatting options is provided, it is applied to all numeric variables of popup.vars. Also, a (named) list of lists can be provided. In that case, each list of formatting options is applied to the named variable.

hover

name of the data variable that specifies the hover labels (view mode only). Set to FALSE to disable hover labels. By default FALSE, unless id is specified. In that case, it is set to id,

id

name of the data variable that specifies the indices of the spatial features. Only used for "view" mode.

options

options passed on to the corresponding opt_<layer_function> function

...

to catch deprecated arguments from version < 4.0

lines.only

should only line geometries of the shape object (defined in tm_shape()) be plotted, or also other geometry types (like polygons)? By default "ifany", which means TRUE in case a geometry collection is specified.

hitbox

Controls whether an invisible interaction layer with a larger clickable area (\"hitbox\") is added on top of the lines.

This can improve click and popup behaviour for thin or densely packed lines by increasing the effective mouse interaction width.

Possible values:

"none"

No additional hitbox layer is added. Lines are clickable only at their visible width.

html
\item{"pmaxX"}{Ensures a minimum interaction width of \code{X} pixels. The hitbox width is computed as \code{pmax(line_width, X)}. For example, \code{"pmax8"} guarantees at least 8 pixels.} \item{"timesX"}{Multiplies the visible line width by \code{X} to compute the interaction width. For example, \code{"times2"} doubles the clickable width.} \item{"auto"}{Automatically: \code{"pmax8"} by default if and only if interactive features are enabled (popup or hover) and lines are thin (median line width < 4) and there are less than 10000 features. Otherwise, \code{"none"} } html

Adding a hitbox improves usability for thin lines but may reduce performance for very large datasets, as an additional invisible layer is rendered.

Details

The visual 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 about visual 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 about facets.

  • The *.scale arguments determine the used scale to map the data values to visual 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 vignette about 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 vignette about legends.

  • The *.chart arguments specify additional charts, specified with tm_chart_, e.g. tm_chart_histogram(). See vignette about 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 visual 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.

See also

Terrain map example

Examples

tm_shape(World_rivers) +
  tm_lines(lwd = "strokelwd",
       lwd.scale = tm_scale_asis(values.scale = 0.2, value.neutral = 2),
       col = "scalerank",
       col.scale = tm_scale_categorical(values = "seaborn.dark"))


tm_shape(World) +
  tm_lines(col = "continent",
       col.scale = tm_scale_categorical(values = "seaborn.dark"),
       lty = "continent",
       lwd = 1.5,
       lty.legend = tm_legend_combine("col"))