In r-tmap/tmap: Thematic Maps

knitr::opts_chunk$set(
  collapse = TRUE,
  fig.width = 8,
  comment = "#>"
)
hook_output <- knitr::knit_hooks$get("output")
knitr::knit_hooks$set(output = function(x, options) {
   lines <- options$output.lines
   if (is.null(lines)) {
     return(hook_output(x, options))  # pass to default hook
   }
   x <- unlist(strsplit(x, "\n"))
   more <- "..."
   if (length(lines)==1) {        # first n lines
     if (length(x) > lines) {
       # truncate the output, but add ....
       x <- c(head(x, lines), more)
     }
   } else {
     x <- c(more, x[lines], more)
   }
   # paste these lines together
   x <- paste(c(x, ""), collapse = "\n")
   hook_output(x, options)
 })

library(tmap)
tmap_options(scale = 0.75)

Layer groups

Via the group and group.control argument in the map layer functions it is possible group layers and (de)select in the leaflet layer control box.

tmap_mode("view")
tm_shape(NLD_dist) +
  tm_polygons(
    fill = "dwelling_value",
    col = NULL,
    fill.scale = tm_scale_intervals(values = "-brewer.rd_yl_bu", breaks = c(75, 150, 250, 500, 750, 1000, 1600)),
    fill.legend = tm_legend("Dwelling value (x 1000)"),
    group = "District data") +
tm_shape(NLD_muni) +
  tm_borders(lwd = 1, col = "black", group = "Municipality borders") +
tm_title("Select and deselect groups") +
tm_shape(NLD_prov, name = "Province borders") +
  tm_borders(lwd = 3) +
tm_view(set_zoom_limits = c(8,14))

Important is that the plotting order of layers is not affected by the grouping, but specified by the z argument. When these are not specified (such as in this example), the order in the plot call is taken (except for tm_basemap() which is always drawn at the bottom).

Note that if the group argument is not specified, such as in the province layer, the group name is inherited from tm_shape().

Switching between layers

tmap_mode("view")
tm_shape(NLD_dist) +
  tm_polygons(
    fill = "dwelling_value",
    col = NULL,
    fill.scale = tm_scale_intervals(values = "-brewer.rd_yl_bu", breaks = c(75, 150, 250, 500, 750, 1000, 1600)),
    fill.legend = tm_legend("Dwelling value (x 1000)"),
    group = "District data",
    group.control = "radio") +
tm_shape(NLD_muni) +
  tm_polygons(
    fill = "dwelling_value",
    col = NULL,
    fill.scale = tm_scale_intervals(values = "-brewer.rd_yl_bu", breaks = c(75, 150, 250, 500, 750, 1000, 1600)),
    fill.legend = tm_legend("Dwelling value (x 1000)"),
    group = "Municipality data",
    group.control = "radio") +
tm_title("Switching between layers") +
tm_shape(NLD_prov) +
  tm_borders(lwd = 3, group.control = "none") +
tm_basemap("OpenStreetMap") +
tm_view(set_zoom_limits = c(8,14))

Zoom-specific map layers

Via tm_group it is possible to set the group.control and moreover to specify at which zoom levels this group is plotted.

tmap_mode("view")
tm_shape(NLD_dist) +
  tm_polygons(
    fill = "dwelling_value",
    fill.scale = tm_scale_intervals(values = "-brewer.rd_yl_bu", breaks = c(75, 150, 250, 500, 750, 1000, 1600)),
    fill.legend = tm_legend("Dwelling value (x 1000)"),
    group = "District") +
tm_shape(NLD_muni) +
  tm_polygons(
    fill = "dwelling_value",
    fill.scale = tm_scale_intervals(values = "-brewer.rd_yl_bu", breaks = c(75, 150, 250, 500, 750, 1000, 1600)),
    fill.legend = tm_legend_hide(),
    group = "Municipality") +
tm_borders(group = "District", lwd = 2) +
tm_title("Zoom in for district level (and out for municipality level)") +
tm_shape(NLD_prov) +
  tm_borders(lwd = 3, group.control = "none") +
tm_group("Municipality", zoom_levels = 8:10) +
tm_group("District", zoom_levels = 11:14) +
tm_view(set_zoom_limits = c(8,14))