Create a line layer consisting of shared boundaries with no attribute data

Usage

ms_innerlines(input, ...)

Arguments

input

input polygons object to convert to inner lines. One of:

geo_json or character polygons;
SpatialPolygons*;
sf or sfc polygons object

...

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. This should be rarely needed, though may be useful when preparing data for D3-based data visualizations (such as plotly::plot_ly()). Default FALSE

Value

lines in the same class as the input layer, but without attributes

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":[[
                  [102,1],[102,2],[103,2],[103,1],[102,1]
                  ]]}},
              {"type":"Feature",
                "properties":{"foo": "b"},
                "geometry":{"type":"Polygon","coordinates":[[
                  [103,1],[103,2],[104,2],[104,1],[103,1]
                  ]]}}]}', class = c("geojson", "json"))

poly <- geojson_sf(poly)
plot(poly)


out <- ms_innerlines(poly)
plot(out)