Add a Spatial Layer to a Leaflet Map

This function adds a spatial layer (e.g., polygons or polylines, or points) to an existing Leaflet map, customizing its appearance with colors, weights, opacity, and fill properties. It dynamically handles different geometry types within the layer.

Usage

add_leaflet_layer(
  map,
  layer,
  group,
  point_marker = "marker",
  show_popup = TRUE
)

Arguments

map

leaflet map object (leaflet object) to which the layer will be added.

layer

sf object representing the spatial layer to add to the map. This object should contain attributes for color, opacity, and fill.

group

character string representing the group name for the layer. This is used for the layers control in the Leaflet map, allowing users to toggle the layer's visibility.

point_marker

character string specifying the type of marker to use for point geometries. Valid options are "marker", "circle", and "popup". Defaults to "marker".

show_popup

Logical. It indicates whether to display popups for features in the layer. Defaults to TRUE.

Value

leaflet map object (leaflet object) with the added layer.

Details

The function differentiates between polygon, polyline, and point geometries within the layer object. Polygons are added using leaflet::addPolygons, polylines are added using leaflet::addPolylines, and points are added using either leaflet::addMarkers, leaflet::addCircleMarkers, or leaflet::addPopups, based on the point_marker parameter. The function also adds the layer's legend to the map, displaying the unique fill colors and corresponding labels from the layer's attributes (only for non-point geometries).

The layer (sf object) provided to this function is expected to include the following attributes in its associated data.frame:

• color: A character or numeric vector specifying the color of the feature (used for polygons and polylines).

• opacity: A numeric value between 0 and 1 indicating the opacity of the feature (used for polygons and polylines).

• fill: A character or numeric vector specifying the fill color of the feature (used for polygons).

• label: A character vector providing a label or description for each feature This label is used as the legend label for polygon and line geometries.

• popup: If show_popup = TRUE, a character vector containing HTML-formatted text

See also

Other interactive mapping: add_visual_param(), map_leaflet_commune(), map_leaflet_multilayer(), set_provider()

Examples

if (FALSE) { # \dontrun{
# Example usage:
map_bg = set_provider("ign_3d")
map = leaflet::leaflet() |>
 leaflet::addTiles(
     urlTemplate = map_bg[["provider"]],
     attribution = map_bg[["attribution"]],
     options = leaflet::tileOptions(opacity = 0.2)
)
map

map = add_leaflet_layer(
    map = map,
    layer = add_visual_param(
        layer = so_ii_limit,
        visual_param = data.frame(
            id = "perimeter",
            label = "perimeter",
            popup = "so-ii perimeter",
            color = "white",
            fill = "transparent",
            opacity = 1
        )
    ),
    group = "perimeter"
)
map

map = add_leaflet_layer(
    map = map,
    layer = add_visual_param(
        layer = so_ii_hydro,
        visual_param = data.frame(
            id = unique(so.ii::so_ii_hydro[["type"]]),
            label = unique(so.ii::so_ii_hydro[["type"]]),
            popup = unique(so.ii::so_ii_hydro[["type"]]),
            color = scales::alpha(c("blue", "red", "dodgerblue"), 0.5), 
            fill = scales::alpha(c("blue", "red", "dodgerblue"), 0.5),
            opacity = 0.5
        ),
        junction = c("type", "id")
    ),
    group = "perimeter"
)
map

random_points = data.frame(
    label = c("point1", "point2", "point3"),
    long = c(3.821011, 3.870760, 3.896732),
    lat = c(43.55250, 43.65147, 43.61877)
)

random_points = sf::st_as_sf(
    x = random_points,
    coords = c("long","lat"),
    crs = sf::st_crs(so_ii_hydro)
)

map = add_leaflet_layer(
    map = map,
    layer = add_visual_param(
        layer = random_points,
        visual_param = data.frame(
            id = unique(random_points[["label"]]),
            label = unique(random_points[["label"]]),
            color = NA, 
            fill = NA,
            opacity = 0.5,
            popup = sprintf("this is random %s", random_points[["label"]])
        ),
        junction = "label"
    ),
    group = "random_points"
)
map
} # }