rmapshaper (version 0.5.0)

ms_lines: Convert polygons to topological boundaries (lines)

Description

Convert polygons to topological boundaries (lines)

Usage

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

Value

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

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"

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)