ms_filter_fields function

Delete fields in the attribute table

Removes all fields except those listed in the fields parameter

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"

Returns

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