Delete fields in the attribute table

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
#> Simple feature collection with 1 feature and 3 fields
#> Geometry type: POLYGON
#> Dimension:     XY
#> Bounding box:  xmin: 102 ymin: 2 xmax: 104 ymax: 4
#> Geodetic CRS:  WGS 84
#>   a b c                       geometry
#> 1 1 2 3 POLYGON ((102 2, 102 4, 104...

# Filter (keep) fields a and b, drop c
out <- ms_filter_fields(poly, c("a", "b"))
out
#> Simple feature collection with 1 feature and 2 fields
#> Geometry type: POLYGON
#> Dimension:     XY
#> Bounding box:  xmin: 102 ymin: 2 xmax: 104 ymax: 4
#> Geodetic CRS:  WGS 84
#>   a b                       geometry
#> 1 1 2 POLYGON ((102 2, 102 4, 104...