Generate Polygon Overlay
Transforms an input 'sf' object into an image overlay for the current height map.
generate_polygon_overlay( geometry, extent, heightmap = NULL, width = NA, height = NA, offset = c(0, 0), data_column_fill = NULL, linecolor = "black", palette = "white", linewidth = 1 )
geometry |
An 'sf' object with POLYGON geometry. |
extent |
A 'raster::Extent' object with the bounding box for the height map used to generate the original map. |
heightmap |
Default 'NULL'. The original height map. Pass this in to extract the dimensions of the resulting overlay automatically. |
width |
Default 'NA'. Width of the resulting overlay. Default the same dimensions as height map. |
height |
Default 'NA'. Width of the resulting overlay. Default the same dimensions as height map. |
offset |
Default 'c(0,0)'. Horizontal and vertical offset to apply to the polygon, in units of 'geometry'. |
data_column_fill |
Default 'NULL'. The column to map the polygon fill color to. |
linecolor |
Default 'black'. Color of the lines. |
palette |
Default 'black'. Single color, named vector color palette, or palette function. If this is a named vector and 'data_column_fill' is not 'NULL', it will map the colors in the vector to the names. If 'data_column_fill' is a numeric column, this will give a continuous mapping. |
linewidth |
Default '1'. Line width. |
Image overlay representing the input polygon data.
#Plot the counties around Monterey Bay, CA
#Only run these examples if the `magick` package is installed.
if ("magick" %in% rownames(utils::installed.packages())) {
generate_polygon_overlay(monterey_counties_sf, palette = rainbow,
extent = attr(montereybay,"extent"), heightmap = montereybay) %>%
plot_map()
#These counties include the water, so we'll plot bathymetry data over the polygon
#data to only include parts of the polygon that fall on land.
water_palette = colorRampPalette(c("darkblue", "dodgerblue", "lightblue"))(200)
bathy_hs = height_shade(montereybay, texture = water_palette)
generate_polygon_overlay(monterey_counties_sf, palette = rainbow,
extent = attr(montereybay,"extent"), heightmap = montereybay) %>%
add_overlay(generate_altitude_overlay(bathy_hs, montereybay, start_transition = 0)) %>%
plot_map()
#Add a semi-transparent hillshade and change the palette, and remove the polygon lines
montereybay %>%
sphere_shade(texture = "bw") %>%
add_overlay(generate_polygon_overlay(monterey_counties_sf,
palette = terrain.colors, linewidth=NA,
extent = attr(montereybay,"extent"), heightmap = montereybay),
alphalayer=0.7) %>%
add_overlay(generate_altitude_overlay(bathy_hs, montereybay, start_transition = 0)) %>%
add_shadow(ray_shade(montereybay,zscale=50),0) %>%
plot_map()
#Map one of the variables in the sf object and use an explicitly defined color palette
county_palette = c("087" = "red", "053" = "blue", "081" = "green",
"069" = "yellow", "085" = "orange", "099" = "purple")
montereybay %>%
sphere_shade(texture = "bw") %>%
add_shadow(ray_shade(montereybay,zscale=50),0) %>%
add_overlay(generate_polygon_overlay(monterey_counties_sf, linecolor="white", linewidth=3,
palette = county_palette, data_column_fill = "COUNTYFP",
extent = attr(montereybay,"extent"), heightmap = montereybay),
alphalayer=0.7) %>%
add_overlay(generate_altitude_overlay(bathy_hs, montereybay, start_transition = 0)) %>%
add_shadow(ray_shade(montereybay,zscale=50),0.5) %>%
plot_map()
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