ms_erase function

Remove features or portions of features that fall inside a specified area

Removes portions of the target layer that fall inside the erasing layer or bounding box.

ms_erase(target, erase = NULL, bbox = NULL, remove_slivers = FALSE, ...)

Arguments

• target: the target layer from which to remove portions. One of:

  • geo_json or character points, lines, or polygons;
  • SpatialPolygons, SpatialLines, SpatialPoints

• erase: the erase layer (polygon). One of:

  • geo_json or character polygons;
  • SpatialPolygons*

• bbox: supply a bounding box instead of an erasing layer to remove from the target layer. Supply as a numeric vector: c(minX, minY, maxX, maxY).

• remove_slivers: Remove tiny sliver polygons created by erasing. (Default FALSE)

• ...: Arguments passed on to apply_mapshaper_commands

  • force_FC: should the output be forced to be a FeatureCollection (or sf object or Spatial*DataFrame) even if there are no attributes? Default TRUE. If FALSE and there are no attributes associated with the geometries, a GeometryCollection (or Spatial object with no dataframe, or sfc) will be output.
  • sys: Should the system mapshaper be used instead of the bundled mapshaper? Gives better performance on large files. Requires the mapshaper node package to be installed and on the PATH.
  • sys_mem: How much memory (in GB) should be allocated if using the system mapshaper (sys = TRUE)? Default 8. Ignored if sys = FALSE. This can also be set globally with the option "mapshaper.sys_mem"
  • quiet: If sys = TRUE, should the mapshaper messages be silenced? Default FALSE. This can also be set globally with the option "mapshaper.sys_quiet"

Returns

erased target in the same format as the input target

Examples

if (rmapshaper:::check_v8_major_version() >= 6L) {
  library(geojsonsf, quietly = TRUE)
  library(sf)

  points <- structure("{\"type\":\"FeatureCollection\",
    \"features\":[{\"type\":\"Feature\",\"properties\":{},
    \"geometry\":{\"type\":\"Point\",\"coordinates\":
    [52.8658,-44.7219]}},{\"type\":\"Feature\",\"properties\":{},
    \"geometry\":{\"type\":\"Point\",\"coordinates\":
    [53.7702,-40.4873]}},{\"type\":\"Feature\",\"properties\":{},
    \"geometry\":{\"type\":\"Point\",\"coordinates\":[55.3204,-37.5579]}},
    {\"type\":\"Feature\",\"properties\":{},\"geometry\":
    {\"type\":\"Point\",\"coordinates\":[56.2757,-37.917]}},
    {\"type\":\"Feature\",\"properties\":{},\"geometry\":
    {\"type\":\"Point\",\"coordinates\":[56.184,-40.6443]}},
    {\"type\":\"Feature\",\"properties\":{},\"geometry\":
    {\"type\":\"Point\",\"coordinates\":[61.0835,-40.7529]}},
    {\"type\":\"Feature\",\"properties\":{},\"geometry\":
    {\"type\":\"Point\",\"coordinates\":[58.0202,-43.634]}}]}",
    class = c("geojson", "json"))
  points <- geojson_sf(points)
  plot(points)

  erase_poly <- structure('{
  "type": "Feature",
  "properties": {},
  "geometry": {
  "type": "Polygon",
  "coordinates": [
  [
  [51, -40],
  [55, -40],
  [55, -45],
  [51, -45],
  [51, -40]
  ]
  ]
  }
  }', class = c("geojson", "json"))
  erase_poly <- geojson_sf(erase_poly)

  out <- ms_erase(points, erase_poly)
  plot(out, add = TRUE)
}