rmapshaper: ms_points – R documentation

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ms_points

Create points from a polygon layer

Description

Can be generated from the polygons by specifying location to be "centroid" or "inner", OR by specifying fields in the attributes of the layer containing x and y coordinates.

Usage

ms_points(
  input,
  location = NULL,
  x = NULL,
  y = NULL,
  force_FC = TRUE,
  sys = FALSE
)

Arguments

`input`	input polygons object to convert to points. One of: `geo_json` or `character` polygons; `geo_list` polygons; `SpatialPolygons*`; `sf` or `sfc` polygons object
`location`	either `"centroid"` or `"inner"`. If `"centroid"`, creates points at the centroid of the largest ring of each polygon feature. if `"inner"`, creates points in the interior of the largest ring of each polygon feature. Inner points are located away from polygon boundaries. Must be `NULL` if `x` and `y` are specified. If left as `NULL` (default), will use centroids.
`x`	name of field containing x coordinate values. Must be `NULL` if `location` is specified.
`y`	name of field containing y coordinate values. Must be `NULL` if `location` is specified.
`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 a `SpatialPoints*` is always the 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.

Value

points in the same class as the input.

Examples

library(geojsonio)
library(sp)

poly <- structure("{\"type\":\"FeatureCollection\",
           \"features\":[{\"type\":\"Feature\",\"properties\":
           {\"x_pos\": 1, \"y_pos\": 2},
           \"geometry\":{\"type\":\"Polygon\",
           \"coordinates\":[[[102,2],[102,4],[104,4],[104,2],[102,2]]]}},
           {\"type\":\"Feature\",\"properties\":{\"x_pos\": 3, \"y_pos\": 4},
           \"geometry\":{\"type\":\"Polygon\",
           \"coordinates\":[[[100,2],[98,4],[101.5,4],[100,2]]]}},
           {\"type\":\"Feature\",\"properties\":{\"x_pos\": 5, \"y_pos\": 6},
           \"geometry\":{\"type\":\"Polygon\",
           \"coordinates\":[[[100,0],[100,1],[101,1],[101,0],[100,0]]]}}]}",
           class = c("json", "geo_json"))

poly <- geojson_sp(poly)
summary(poly)
plot(poly)

# Convert to points using centroids
out <- ms_points(poly, location = "centroid")
summary(out)
plot(out)

# Can also specify locations using attributes in the data
out <- ms_points(poly, x = "x_pos", y = "y_pos")
summary(out)
plot(out)

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