rmapshaper: ms_dissolve – R documentation

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ms_dissolve

Aggregate shapes in a polygon or point layer.

Description

Aggregates using specified field, or all shapes if no field is given. For point layers, replaces a group of points with their centroid.

Usage

ms_dissolve(
  input,
  field = NULL,
  sum_fields = NULL,
  copy_fields = NULL,
  weight = NULL,
  snap = TRUE,
  force_FC = TRUE,
  sys = FALSE
)

Arguments

`input`	spatial object to dissolve. One of: `geo_json` or `character` points or polygons; `geo_list` points or polygons; `SpatialPolygons`, or `SpatialPoints`
`field`	the field to dissolve on
`sum_fields`	fields to sum
`copy_fields`	fields to copy. The first instance of each field will be copied to the aggregated feature.
`weight`	Name of an attribute field for generating weighted centroids (points only).
`snap`	Snap together vertices within a small distance threshold to fix small coordinate misalignment in adjacent polygons. Default `TRUE`.
`force_FC`	should the output be forced to be a `FeatureCollection` even if there are no attributes? Default `TRUE`. `FeatureCollections` are more compatible with `rgdal::readOGR` and `geojsonio::geojson_sp`. If `FALSE` and there are no attributes associated with the geometries, a `GeometryCollection` will be output. Ignored for `Spatial` objects, as the output is always the same class as the input.
`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.

Value

the same class as the input

Examples

library(geojsonio)
library(sp)

poly <- structure('{"type":"FeatureCollection",
  "features":[
  {"type":"Feature",
  "properties":{"a": 1, "b": 2},
  "geometry":{"type":"Polygon","coordinates":[[
  [102,2],[102,3],[103,3],[103,2],[102,2]
  ]]}}
  ,{"type":"Feature",
  "properties":{"a": 5, "b": 3},
  "geometry":{"type":"Polygon","coordinates":[[
  [100,0],[100,1],[101,1],[101,0],[100,0]
  ]]}}]}', class = c("json", "geo_json"))
poly <- geojson_sp(poly)
plot(poly)
length(poly)
poly@data

# Dissolve the polygon
out <- ms_dissolve(poly)
plot(out)
length(out)
out@data

# Dissolve and summing columns
out <- ms_dissolve(poly, sum_fields = c("a", "b"))
plot(out)
out@data

rmapshaper

Client for 'mapshaper' for 'Geospatial' Operations

v0.4.4

MIT + file LICENSE

Authors

Andy Teucher [aut, cre], Kenton Russell [aut] (JavaScript support), Matthew Bloch [cph] (mapshaper Javascript library)

Initial release