% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/tm_layers_lines.R
\name{tm_lines}
\alias{tm_lines}
\alias{opt_tm_lines}
\title{Map layer: lines}
\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{
\item{col, col.scale, col.legend, col.chart, col.free}{Visual variable that determines the color. See details.}

\item{lwd, lwd.scale, lwd.legend, lwd.chart, lwd.free}{Visual variable that determines the line width. See details.}

\item{lty, lty.scale, lty.legend, lty.chart, lty.free}{Visual variable that determines the line type. See details.}

\item{col_alpha, col_alpha.scale, col_alpha.legend, col_alpha.chart, col_alpha.free}{Visual variable that determines the color transparency. See details.}

\item{linejoin, lineend}{line join and line end. See \link[grid:gpar]{gpar()} for details.}

\item{plot.order}{Specification in which order the spatial features are drawn. See \code{\link[=tm_plot_order]{tm_plot_order()}} for details.}

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

\item{group}{Name of the group to which this layer belongs. This is only
relevant in view mode, where layer groups can be switched (see \code{group.control})}

\item{group.control}{In view mode, the group control determines how layer groups
can be switched on and off. Options: \code{"radio"} for radio buttons
(meaning only one group can be shown), \code{"check"} for check boxes
(so multiple groups can be shown), and \code{"none"} for no control
(the group cannot be (de)selected).}

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

\item{popup.format}{list of formatting options for the popup values. Output of \code{\link[=tm_label_format]{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 \code{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.}

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

\item{id}{name of the data variable that specifies the indices of the spatial
features. Only used for \code{"view"} mode.}

\item{options}{options passed on to the corresponding \verb{opt_<layer_function>} function}

\item{...}{to catch deprecated arguments from version < 4.0}

\item{lines.only}{should only line geometries of the shape object (defined in \code{\link[=tm_shape]{tm_shape()}}) be plotted, or also other geometry types (like polygons)? By default \code{"ifany"}, which means \code{TRUE} in case a geometry collection is specified.}

\item{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:
\describe{
\item{"none"}{No additional hitbox layer is added. Lines are clickable
only at their visible width.}

\if{html}{\out{<div class="sourceCode">}}\preformatted{\\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"} \}
}\if{html}{\out{</div>}}

}

Adding a hitbox improves usability for thin lines but may reduce
performance for very large datasets, as an additional invisible
layer is rendered.}
}
\description{
Map layer that draws lines. Supported visual variables are: \code{col} (the color), \code{lwd} (line width), \code{lty} (line type), and \code{col_alpha} (color alpha transparency).
}
\details{
The visual variable arguments (e.g. \code{col}) can be specified with a data
variable name (e.g., a spatial vector attribute or a raster layer of the object
specified in \code{\link[=tm_shape]{tm_shape()}}), with a visual value (for \code{col}, a color is expected), or with a geometry-derived variable (see below).
See \href{https://r-tmap.github.io/tmap/articles/basics_vv}{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 \code{\link[=tm_facets]{tm_facets()}}.
See \href{https://r-tmap.github.io/tmap/articles/basics_facets}{vignette about facets}.
\itemize{
\item The \verb{*.scale} arguments determine the used scale to map the data values to
visual variable values. These can be specified with one of the available
\verb{tm_scale_*()} functions. The default is specified by the tmap option (\code{\link[=tm_options]{tm_options()}}) \code{scales.var}.
See \href{https://r-tmap.github.io/tmap/articles/basics_scales}{vignette about scales}.
\item The \verb{*.legend} arguments determine the used legend, specified with \code{\link[=tm_legend]{tm_legend()}}.
The default legend and its settings are determined by the tmap options (\code{\link[=tm_options]{tm_options()}}) \code{legend.} .
See \href{https://r-tmap.github.io/tmap/articles/basics_legends}{vignette about legends}.
\item The \verb{*.chart} arguments specify additional charts, specified with \code{tm_chart_}, e.g. \code{\link[=tm_chart_histogram]{tm_chart_histogram()}}.
See \href{https://r-tmap.github.io/tmap/articles/basics_charts}{vignette about charts}.
\item The \verb{*.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 \code{\link[=tm_facets]{tm_facets()}}).
There are maximally three facet dimensions: rows, columns, and pages. This only
applies for a facet grid (\code{\link[=tm_facets_grid]{tm_facets_grid()}}). For instance, \code{col.free = c(TRUE, FALSE, FALSE)}
means that for the visual variable \code{col}, each row of facets will have its own
scale, and therefore its own legend. For facet wraps and stacks
(\code{\link[=tm_facets_wrap]{tm_facets_wrap()}} and \code{\link[=tm_facets_stack]{tm_facets_stack()}}) there is only one facet dimension,
so the \verb{*.free} argument requires only one logical value.
}

Currently, three geometry-derived variables are implemented:
\itemize{
\item \code{"AREA"} (polygons only), which uses the feature area;
\item \code{"LENGTH"} (lines only), which uses the feature length; and
\item \code{"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 \code{\link[sf:geos_measures]{sf::st_area()}}, \code{\link[sf:geos_measures]{sf::st_length()}}, or
\code{\link[tmaptools:map_coloring]{tmaptools::map_coloring()}}, and use the resulting values instead.
}
\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"))
}
\seealso{
\href{https://r-tmap.github.io/tmap/articles/examples_terrain}{Terrain map example}
}
