ms_lines: Convert polygons to topological boundaries (lines)

In ateucher/rmapshaper: Client for 'mapshaper' for 'Geospatial' Operations

Convert polygons to topological boundaries (lines)

Description

Convert polygons to topological boundaries (lines)

Usage

ms_lines(input, fields = NULL, ...)

Arguments

input	input polygons object to convert to inner lines. One of: geo_json or character polygons; SpatialPolygons*; sf or sfc polygons object
fields	character vector of field names. If left as NULL (default), external (unshared) boundaries are attributed as TYPE 0 and internal (shared) boundaries are TYPE 1. Giving a field name adds an intermediate level of hierarchy at TYPE 1, with the lowest-level internal boundaries set to TYPE 2. Supplying a character vector of field names adds additional levels of hierarchy.
...	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" gj2008 Generate output that is consistent with the pre-RFC 7946 GeoJSON spec (dating to 2008). Polygon rings are CW and holes are CCW, which is the opposite of the default RFC 7946-compatible output.

Value

topological boundaries as lines, in the same class as the input

Examples

library(geojsonsf)
library(sf)

poly <- structure('{"type":"FeatureCollection",
             "features":[
             {"type":"Feature",
             "properties":{"foo": "a"},
             "geometry":{"type":"Polygon","coordinates":[[
             [102,2],[102,3],[103,3],[103,2],[102,2]
             ]]}}
             ,{"type":"Feature",
             "properties":{"foo": "a"},
             "geometry":{"type":"Polygon","coordinates":[[
             [103,3],[104,3],[104,2],[103,2],[103,3]
             ]]}},
             {"type":"Feature",
             "properties":{"foo": "b"},
             "geometry":{"type":"Polygon","coordinates":[[
             [102.5,1],[102.5,2],[103.5,2],[103.5,1],[102.5,1]
             ]]}}]}', class = c("geojson", "json"))

poly <- geojson_sf(poly)
summary(poly)
plot(poly)

out <- ms_lines(poly)
summary(out)
plot(out)

ateucher/rmapshaper documentation built on Nov. 2, 2023, 4:23 p.m.