Use ggforce to create an annotation layer using simple feature data

Use ggforce::geom_mark_rect(), ggforce::geom_mark_circle(), ggforce::geom_mark_ellipse(), or ggforce::geom_mark_hull() to annotate simple feature objects. This function modifies the geometry and sets the stat to "st_coordinates" to make it easy to use these annotation geoms with simple feature objects.

Usage

layer_marked(
  data,
  fn = NULL,
  mapping = NULL,
  label_col = NULL,
  desc_col = NULL,
  geom = NULL,
  center = FALSE,
  font_family = NULL,
  font_face = c("bold", "plain"),
  font_color = NULL,
  expand = ggplot2::unit(5, "mm"),
  radius = expand,
  stat = "sf_coordinates",
  drop_shadow = FALSE,
  shadow_params = list(x_offset = 5, y_offset = 5, sigma = 0.5, ...),
  ...
)

Arguments

data: A sf, sfc, or bbox object that can be converted with sfext::as_sf
fn: Function to apply to data before passing to geom, typically a predicate or filter to define area for annotation. A filter can also be passed to any of the ggforce functions using the filter aesthetic. Default: NULL
mapping: Aesthetic mapping to pass to geom, Default: NULL
label_col: Label column name
desc_col: Column name to use for description. Defaults to NULL.
geom: geom to use for layer (options include "rect", "circle", "ellipse", or "hull"), Default: NULL
center: If FALSE, use sfext::st_cast_ext MULTIPOLYGON and POLYGON data to POINT; If TRUE, use sfext::st_center use centroid as the feature geometry. Defaults to FALSE.
font_family, font_face, font_color: Parameters passed to label.family, label.fontface, and label.colour. If NULL, values are set to match ggplot2::geom_label defaults. Defaults to NULL.
expand: A numeric or unit vector of length one, specifying the expansion amount. Negative values will result in contraction instead. If the value is given as a numeric it will be understood as a proportion of the plot area width.
radius: As expand but specifying the corner radius.
stat: stat to pass to ggforce function; defaults to "sf_coordinates"
drop_shadow: If TRUE, use ggfx::with_shadow() to add a drop shadow to the label layer with shadow_params. Defaults to FALSE.
shadow_params: Parameters passed to ggfx::with_shadow() if drop_shadow = TRUE. Defaults to list(x_offset = 5, y_offset = 5, sigma = 0.5).
...: Additional parameters passed to ggforce::geom_mark_rect(), ggforce::geom_mark_circle(), ggforce::geom_mark_ellipse(), or ggforce::geom_mark_hull() or on to ggplot2::layer()

Geometry conversion for MULTIPOLYGON or POLYGON data

If cast is FALSE and the data geometry type is MULTIPOLYGON or POLYGON, the annotation uses a centroid for the annotation geometry. If cast is TRUE, the data is converted to POINT geometry using sfext::st_cast_ext() and the modified geometry passed on to selected geom.

Setting label and description

Labels and descriptions can be included in the aesthetic mapping for the layer consistent with the standard documented approaches for all four functions.

Labels and descriptions also can be set in two non-standard ways:

Setting label_col and/or or desc_col to character strings with the column names for labels and/or descriptions
Setting label_col and/or desc_col with the value of the label/description

If the first approach is used, label_col and desc_col can also can be created or modified by a function provided to the fn parameter. Otherwise, the columns must be present in the data to work. If the second approach is used, the length and order of vector provided to label_col and/or desc_col must match that length and order of the data (after the fn is applied).

Examples

if (FALSE) {
if (interactive()) {
  # Mark the 12th Council District on a Baltimore neighborhood basemap
  ggplot::ggplot() +
    layer_location_data(
      data = "neighborhoods",
      package = "mapbaltimore"
    ) +
    layer_marked(
      data = getdata::get_location(
        type = "council district",
        name = "District 12",
        package = "mapbaltimore"
      ),
      geom = "hull",
      color = "red",
      size = 1.5
    )
}
}