Help for package rmapshaper

Type:

Package

Title:

Client for 'mapshaper' for 'Geospatial' Operations

Version:

0.5.0

Description:

Edit and simplify 'geojson', 'Spatial', and 'sf' objects. This is wrapper around the 'mapshaper' 'JavaScript' library by Matthew Bloch https://github.com/mbloch/mapshaper/ to perform topologically-aware polygon simplification, as well as other operations such as clipping, erasing, dissolving, and converting 'multi-part' to 'single-part' geometries.

License:

MIT + file LICENSE

URL:

https://github.com/ateucher/rmapshaper

BugReports:

https://github.com/ateucher/rmapshaper/issues

Imports:

methods, geojsonsf (≥ 2.0.2), jsonify (≥ 1.2.0), readr (≥ 2.1.0), sf (≥ 1.0.0), sp (≥ 1.4-0), V8 (≥ 4.0.0)

Suggests:

knitr, magrittr, rmarkdown, testthat (≥ 3.0.0), jsonlite, covr, units, withr

VignetteBuilder:

knitr

Encoding:

UTF-8

RoxygenNote:

7.2.3

Config/testthat/edition:

NeedsCompilation:

Packaged:

2023-04-10 21:55:00 UTC; andyteucher

Author:

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

Maintainer:

Andy Teucher <andy.teucher@gmail.com>

Repository:

CRAN

Date/Publication:

2023-04-11 02:20:02 UTC

Apply a mapshaper command string to a geojson object

Description

Apply a mapshaper command string to a geojson object

Usage

apply_mapshaper_commands(
  data,
  command,
  force_FC = TRUE,
  sys = FALSE,
  sys_mem = getOption("mapshaper.sys_mem", default = 8),
  quiet = getOption("mapshaper.sys_quiet", default = FALSE)
)

Arguments

data

character containing geojson or path to geojson file. If a file path, sys must be true.

command

valid mapshaper command string

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"

Value

geojson

Examples


nc <- sf::read_sf(system.file("gpkg/nc.gpkg", package = "sf"))
rmapshaper::apply_mapshaper_commands(geojsonsf::sf_geojson(nc), "-clean")

Check the system mapshaper

Description

Check the system mapshaper

Usage

check_sys_mapshaper(command = "mapshaper-xl", verbose = TRUE)

Arguments

command

either "mapshaper-xl" (default) or "mapshaper"

verbose

Print a message stating mapshaper's current version? Default TRUE

Value

character path to mapshaper executable if appropriate version is installed, otherwise throws an error

Drop features from a `geo_json` FeatureCollection with null geometries

Description

Drop features from a geo_json FeatureCollection with null geometries

Usage

drop_null_geometries(x)

Arguments

x

a geo_json FeatureCollection

Value

a geo_json FeatureCollection with Features with null geometries removed

Remove features or portions of features that fall outside a clipping area.

Description

Removes portions of the target layer that fall outside the clipping layer or bounding box.

Usage

ms_clip(target, clip = NULL, bbox = NULL, remove_slivers = FALSE, ...)

Arguments

target

the target layer from which to remove portions. One of:

geo_json or character points, lines, or polygons;
SpatialPolygons, SpatialLines, SpatialPoints;
sf or sfc points, lines, or polygons object

clip

the clipping layer (polygon). One of:

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

bbox

supply a bounding box instead of a clipping layer to extract from the target layer. Supply as a numeric vector: c(minX, minY, maxX, maxY).

remove_slivers

Remove tiny sliver polygons created by clipping. (Default FALSE)

...

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"

Value

clipped target in the same class as the input target

Examples


if (rmapshaper:::check_v8_major_version() >= 6L) {
  library(geojsonsf, quietly = TRUE)
  library(sf)

  poly <- structure("{\"type\":\"FeatureCollection\",
    \"features\":[{\"type\":\"Feature\",\"properties\":{},
    \"geometry\":{\"type\":\"Polygon\",\"coordinates\":
    [[[52.8658,-44.7219],[53.7702,-40.4873],[55.3204,-37.5579],
    [56.2757,-37.917],[56.184,-40.6443],[61.0835,-40.7529],
    [58.0202,-43.634],[61.6699,-45.0678],[62.737,-46.2841],
    [55.7763,-46.2637],[54.9742,-49.1184],[52.799,-45.9386],
    [52.0329,-49.5677],[50.1747,-52.1814],[49.0098,-52.3641],
    [52.7068,-45.7639],[43.2278,-47.1908],[48.4755,-45.1388],
    [50.327,-43.5207],[48.0804,-41.2784],[49.6307,-40.6159],
    [52.8658,-44.7219]]]}}]}", class = c("geojson", "json"))
  poly <- geojson_sf(poly)
  plot(poly)

  clip_poly <- structure('{
  "type": "Feature",
  "properties": {},
  "geometry": {
  "type": "Polygon",
  "coordinates": [
  [
  [51, -40],
  [55, -40],
  [55, -45],
  [51, -45],
  [51, -40]
  ]
  ]
  }
  }', class = c("geojson", "json"))
  clip_poly <- geojson_sf(clip_poly)
  plot(clip_poly)

  out <- ms_clip(poly, clip_poly)
  plot(out, add = TRUE)
}

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,
  ...
)

Arguments

input

spatial object to dissolve. One of:

geo_json or character 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.

...

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"

Value

the same class as the input

Examples

library(geojsonsf)
library(sf)

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("geojson", "json"))
poly <- geojson_sf(poly)
plot(poly)
length(poly)
poly

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

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

Remove features or portions of features that fall inside a specified area

Description

Removes portions of the target layer that fall inside the erasing layer or bounding box.

Usage

ms_erase(target, erase = NULL, bbox = NULL, remove_slivers = FALSE, ...)

Arguments

target

the target layer from which to remove portions. One of:

geo_json or character points, lines, or polygons;
SpatialPolygons, SpatialLines, SpatialPoints

erase

the erase layer (polygon). One of:

geo_json or character polygons;
SpatialPolygons*

bbox

supply a bounding box instead of an erasing layer to remove from the target layer. Supply as a numeric vector: c(minX, minY, maxX, maxY).

remove_slivers

Remove tiny sliver polygons created by erasing. (Default FALSE)

...

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"

Value

erased target in the same format as the input target

Examples

if (rmapshaper:::check_v8_major_version() >= 6L) {
  library(geojsonsf, quietly = TRUE)
  library(sf)

  points <- structure("{\"type\":\"FeatureCollection\",
    \"features\":[{\"type\":\"Feature\",\"properties\":{},
    \"geometry\":{\"type\":\"Point\",\"coordinates\":
    [52.8658,-44.7219]}},{\"type\":\"Feature\",\"properties\":{},
    \"geometry\":{\"type\":\"Point\",\"coordinates\":
    [53.7702,-40.4873]}},{\"type\":\"Feature\",\"properties\":{},
    \"geometry\":{\"type\":\"Point\",\"coordinates\":[55.3204,-37.5579]}},
    {\"type\":\"Feature\",\"properties\":{},\"geometry\":
    {\"type\":\"Point\",\"coordinates\":[56.2757,-37.917]}},
    {\"type\":\"Feature\",\"properties\":{},\"geometry\":
    {\"type\":\"Point\",\"coordinates\":[56.184,-40.6443]}},
    {\"type\":\"Feature\",\"properties\":{},\"geometry\":
    {\"type\":\"Point\",\"coordinates\":[61.0835,-40.7529]}},
    {\"type\":\"Feature\",\"properties\":{},\"geometry\":
    {\"type\":\"Point\",\"coordinates\":[58.0202,-43.634]}}]}",
    class = c("geojson", "json"))
  points <- geojson_sf(points)
  plot(points)

  erase_poly <- structure('{
  "type": "Feature",
  "properties": {},
  "geometry": {
  "type": "Polygon",
  "coordinates": [
  [
  [51, -40],
  [55, -40],
  [55, -45],
  [51, -45],
  [51, -40]
  ]
  ]
  }
  }', class = c("geojson", "json"))
  erase_poly <- geojson_sf(erase_poly)

  out <- ms_erase(points, erase_poly)
  plot(out, add = TRUE)
}

Convert multipart lines or polygons to singlepart

Description

For objects of class Spatial (e.g., SpatialPolygonsDataFrame), you may find it faster to use sp::disaggregate.

Usage

ms_explode(input, ...)

Arguments

input

One of:

geo_json or character multipart lines, or polygons;
multipart SpatialPolygons, SpatialLines;
sf or sfc multipart lines, or 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"

Details

There is currently no method for SpatialMultiPoints

Value

same class as input

Examples

library(geojsonsf)
library(sf)

poly <- "{\"type\":\"FeatureCollection\",\"features\":
          [\n{\"type\":\"Feature\",\"geometry\":{\"type\":
          \"MultiPolygon\",\"coordinates\":[[[[102,2],[102,3],
          [103,3],[103,2],[102,2]]],[[[100,0],[100,1],[101,1],
          [101,0],[100,0]]]]},\"properties\":{\"a\":0}}\n]}"

poly <- geojson_sf(poly)
plot(poly)
length(poly)
poly

# Explode the polygon
out <- ms_explode(poly)
plot(out)
length(out)
out

Delete fields in the attribute table

Description

Removes all fields except those listed in the fields parameter

Usage

ms_filter_fields(input, fields, ...)

Arguments

input

spatial object to filter fields on. One of:

geo_json or character points, lines, or polygons;
SpatialPolygonsDataFrame, SpatialLinesDataFrame, SpatialPointsDataFrame;
sf object

fields

character vector of fields to retain.

...

Arguments passed on to apply_mapshaper_commands

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"

Value

object with only specified attributes retained, in the same class as the input

Examples

library(geojsonsf)
library(sf)

poly <- structure("{\"type\":\"FeatureCollection\",
                  \"features\":[{\"type\":\"Feature\",
                  \"properties\":{\"a\": 1, \"b\":2, \"c\": 3},
                  \"geometry\":{\"type\":\"Polygon\",
                  \"coordinates\":[[[102,2],[102,4],[104,4],[104,2],[102,2]]]}}]}",
                  class = c("geojson", "json"))
poly <- geojson_sf(poly)
poly

# Filter (keep) fields a and b, drop c
out <- ms_filter_fields(poly, c("a", "b"))
out

Remove small detached polygons (islands)

Description

Remove small detached polygons, keeping those with a minimum area and/or a minimum number of vertices. Optionally remove null geometries.

Usage

ms_filter_islands(
  input,
  min_area = NULL,
  min_vertices = NULL,
  drop_null_geometries = TRUE,
  ...
)

Arguments

input

spatial object to filter. One of:

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

min_area

minimum area of polygons to retain. Area is calculated using planar geometry, except for the area of unprojected polygons, which is calculated using spherical geometry in units of square meters.

min_vertices

minimum number of vertices in polygons to retain.

drop_null_geometries

should features with empty geometries be dropped? Default TRUE. Ignored for SpatialPolyons*, as it is always TRUE.

...

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"

Value

object with only specified features retained, in the same class as the input

Examples

library(geojsonsf)
library(sf)

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

poly <- geojson_sf(poly)
plot(poly)

out <- ms_filter_islands(poly, min_area = 12391399903)
plot(out)

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

Description

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"

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)

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"

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)

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, ...)

Arguments

input

input polygons object to convert to points. One of:

geo_json or character 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.

...

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"

Value

points in the same class as the input.

Examples

library(geojsonsf)
library(sf)

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("geojson", "json"))

poly <- geojson_sf(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)

Topologically-aware geometry simplification.

Description

Uses mapshaper to simplify polygons.

Usage

ms_simplify(
  input,
  keep = 0.05,
  method = NULL,
  weighting = 0.7,
  keep_shapes = FALSE,
  no_repair = FALSE,
  snap = TRUE,
  explode = FALSE,
  drop_null_geometries = TRUE,
  snap_interval = NULL,
  ...
)

Arguments

input

spatial object to simplify. One of:

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

keep

proportion of points to retain (0-1; default 0.05)

method

simplification method to use: "vis" for Visvalingam algorithm, or "dp" for Douglas-Peuker algorithm. If left as NULL (default), uses Visvalingam simplification but modifies the area metric by underweighting the effective area of points at the vertex of more acute angles, resulting in a smoother appearance. See this https://github.com/mbloch/mapshaper/wiki/Simplification-Tipslink for more information.

weighting

Coefficient for weighting Visvalingam simplification (default is 0.7). Higher values produce smoother output. weighting=0 is equivalent to unweighted Visvalingam simplification.

keep_shapes

Prevent small polygon features from disappearing at high simplification (default FALSE)

no_repair

disable intersection repair after simplification (default FALSE).

snap

Snap together vertices within a small distance threshold to fix small coordinate misalignment in adjacent polygons. Default TRUE.

explode

Should multipart polygons be converted to singlepart polygons? This prevents small shapes from disappearing during simplification if keep_shapes = TRUE. Default FALSE

drop_null_geometries

should Features with null geometries be dropped? Ignored for Spatial* objects, as it is always TRUE.

snap_interval

Specify snapping distance in source units, must be a numeric. Default NULL

...

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"

Value

a simplified representation of the geometry in the same class as the input

Examples

# With a simple geojson object
poly <- structure('{
 "type": "Feature",
 "properties": {},
 "geometry": {
   "type": "Polygon",
   "coordinates": [[
     [-70.603637, -33.399918],
     [-70.614624, -33.395332],
     [-70.639343, -33.392466],
     [-70.659942, -33.394759],
     [-70.683975, -33.404504],
     [-70.697021, -33.419406],
     [-70.701141, -33.434306],
     [-70.700454, -33.446339],
     [-70.694274, -33.458369],
     [-70.682601, -33.465816],
     [-70.668869, -33.472117],
     [-70.646209, -33.473835],
     [-70.624923, -33.472117],
     [-70.609817, -33.468107],
     [-70.595397, -33.458369],
     [-70.587158, -33.442901],
     [-70.587158, -33.426283],
     [-70.590591, -33.414248],
     [-70.594711, -33.406224],
     [-70.603637, -33.399918]
   ]]
 }
}', class = c("geojson", "json"))

ms_simplify(poly, keep = 0.1)

# With an sf object

poly_sf <- geojsonsf::geojson_sf(poly)
ms_simplify(poly_sf, keep = 0.5)

rmapshaper: Client for 'mapshaper' for 'Geospatial' Operations

Description

Edit and simplify 'geojson', 'Spatial', and 'sf' objects. This is wrapper around the 'mapshaper' 'javascript' library by Matthew Bloch https://github.com/mbloch/mapshaper/ to perform topologically-aware polygon simplification, as well as other operations such as clipping, erasing, dissolving, and converting 'multi-part' to 'single-part' geometries.

rmapshaper functions

All functions

ms_simplify - simplify polygons or lines
ms_clip - clip an area out of a layer using a polygon layer or a bounding box. Works on polygons, lines, and points
ms_erase - erase an area from a layer using a polygon layer or a bounding box. Works on polygons, lines, and points
ms_dissolve - aggregate polygon features, optionally specifying a field to aggregate on. If no field is specified, will merge all polygons into one.
ms_explode - convert multipart shapes to single part. Works with polygons, lines, and points in geojson format, but currently only with polygons and lines in the Spatial classes (not SpatialMultiPoints and SpatialMultiPointsDataFrame).
ms_lines - convert polygons to topological boundaries (lines)
ms_innerlines - convert polygons to shared inner boundaries (lines)
ms_points - create points from a polygon layer
ms_filter_fields - Remove fields from the attributes
ms_filter_islands - Remove small detached polygons

Author(s)

Andy Teucher andy.teucher@gmail.com

Apply a mapshaper command string to a geojson object

Description

Usage

Arguments

Value

Examples

Check the system mapshaper

Description

Usage

Arguments

Value

Drop features from a geo_json FeatureCollection with null geometries

Description

Usage

Arguments

Value

Remove features or portions of features that fall outside a clipping area.

Description

Usage

Arguments

Value

Examples

Aggregate shapes in a polygon or point layer.

Description

Usage

Arguments

Value

Examples

Remove features or portions of features that fall inside a specified area

Description

Usage

Arguments

Value

Examples

Convert multipart lines or polygons to singlepart

Description

Usage

Arguments

Details

Value

Examples

Delete fields in the attribute table

Description

Usage

Arguments

Value

Examples

Remove small detached polygons (islands)

Description

Usage

Arguments

Value

Examples

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

Description

Usage

Arguments

Value

Examples

Convert polygons to topological boundaries (lines)

Description

Usage

Arguments

Value

Examples

Create points from a polygon layer

Description

Usage

Arguments

Value

Examples

Topologically-aware geometry simplification.

Description

Usage

Arguments

Value

Examples

rmapshaper: Client for 'mapshaper' for 'Geospatial' Operations

Description

rmapshaper functions

Drop features from a `geo_json` FeatureCollection with null geometries