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Format simple feature data

Source: R/format_sf_data.R
format_sf_data.Rd

The main format_sf_data function is a wrapper for the following common steps in transforming an sf object and preparing for mapping or analysis:

Usage

format_sf_data(
  x,
  crs = getOption("getdata.crs", default = 3857),
  erase_data = NULL,
  dTolerance = NULL,
  smooth = FALSE,
  sf_col = NULL,
  sf_req = TRUE,
  ...
)

erase_data(x, erase_data = NULL)

Arguments

x

A sf object or, if sf_req is FALSE, any object that can be converted to an sf object with sfext::as_sf.

crs

Coordinate reference system for returned data, Default: getOption("getdata.crs", default = 3857)

erase_data

A sf, sfc, or bbox object with geometry that should be erased from the data, Default: NULL

dTolerance

numeric; tolerance parameter, specified for all or for each feature geometry. If you run st_simplify, the input data is specified with long-lat coordinates and sf_use_s2() returns TRUE, then the value of dTolerance must be specified in meters.

smooth

If TRUE, smooth data with smoothr::smooth using default method and parameters, Default: FALSE.

sf_col

Name to use for output sf column, Default: 'geometry'.

sf_req

If TRUE, data must be a sf object. If FALSE, data is passed to sfext::as_sf to convert data to an sf object.

...

Additional parameters passed to format_data

Value

A sf object with columns and geometry modified based parameters.

Details

  • Convert data to an sf object with sfext::as_sf if sf_req is FALSE

  • Make data valid with sf::st_make_valid if needed

  • Format data with format_data using the ... parameters

  • Erase any data overlapping with erase_data (suggested for use with water or open space)

  • Simplify geometry with sf::st_simplify if dTolerance is provided

  • Smooth geometry with smoothr::smooth if smooth is TRUE

  • Rename the sf column to match sf_col (defaults to "geometry")

The helper functions for format_sf_data and additional formatting functions for sf data are described in the details.

Helper functions for format_sf_data:

  • erase_data: erase intersection of x and erase_data (validity of erase_data checked before sfext::st_erase and for x after completing the operation.

  • rename_sf_col: Rename sf column.

  • relocate_sf_col: Relocate sf column after selected columns (defaults to dplyr::everything()).

Examples

library(sf)
#> Linking to GEOS 3.10.2, GDAL 3.4.1, PROJ 8.2.1; sf_use_s2() is TRUE

nc <- read_sf(system.file("shape/nc.shp", package = "sf"))
nc_county <- nc[2,]

# Transform coordinate reference system
st_crs(nc)$epsg
#> [1] 4267
st_crs(format_sf_data(nc, crs = 3857))$epsg
#> [1] 3857

# Simplify and smooth geometry
plot(nc_county, max.plot = 1)

nc_county_simple <- format_sf_data(nc_county, dTolerance = 5000, smooth = TRUE)
plot(nc_county_simple, max.plot = 1)


# Erase data
nc_co_water <- get_tigris_data(type = "area water", state = "NC", county = nc_county$NAME)
#> Retrieving data for the year 2021
#> 
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nc_county_erased <- format_sf_data(nc_county, erase_data = nc_co_water)
plot(nc_county_erased, max.plot = 1)


# If sf_req is set to FALSE, use any object that can be converted with sfext::as_sf
nc_bbox <- st_bbox(nc)
plot(format_sf_data(nc_bbox, erase_data = nc_county_simple, sf_req = FALSE))