sf: st_transform – R documentation

Pricing

Become an expert in R — Interactive courses, Cheat Sheets, certificates and more!

Get Started for Free

Documentation

st_transform

Transform or convert coordinates of simple feature

Description

Transform or convert coordinates of simple feature

Usage

st_transform(x, crs, ...)

## S3 method for class 'sfc'
st_transform(
  x,
  crs = st_crs(x),
  ...,
  aoi = numeric(0),
  pipeline = character(0),
  reverse = FALSE,
  desired_accuracy = -1,
  allow_ballpark = TRUE,
  partial = TRUE,
  check = FALSE
)

## S3 method for class 'sf'
st_transform(x, crs = st_crs(x), ...)

## S3 method for class 'sfg'
st_transform(x, crs = st_crs(x), ...)

st_wrap_dateline(x, options, quiet)

## S3 method for class 'sfc'
st_wrap_dateline(x, options = "WRAPDATELINE=YES", quiet = TRUE)

## S3 method for class 'sf'
st_wrap_dateline(x, options = "WRAPDATELINE=YES", quiet = TRUE)

## S3 method for class 'sfg'
st_wrap_dateline(x, options = "WRAPDATELINE=YES", quiet = TRUE)

sf_proj_info(type = "proj", path)

Arguments

`x`	object of class sf, sfc or sfg
`crs`	target coordinate reference system: object of class 'crs', or input string for st_crs
`...`	ignored
`aoi`	area of interest, in degrees: WestLongitude, SouthLatitude, EastLongitude, NorthLatitude
`pipeline`	character; coordinate operation pipeline, for overriding the default operation
`reverse`	boolean; has only an effect when `pipeline` is defined: if `TRUE`, the inverse operation of the pipeline is applied
`desired_accuracy`	numeric; Only coordinate operations that offer an accuracy of at least the one specified will be considered; a negative value disables this feature (requires GDAL >= 3.3)
`allow_ballpark`	logical; are ballpark (low accuracy) transformations allowed? (requires GDAL >= 3.3)
`partial`	logical; allow for partial projection, if not all points of a geometry can be projected (corresponds to setting environment variable `OGR_ENABLE_PARTIAL_REPROJECTION` to `TRUE`)
`check`	logical; if `TRUE`, perform a sanity check on resulting polygons
`options`	character; should have "WRAPDATELINE=YES" to function; another parameter that is used is "DATELINEOFFSET=10" (where 10 is the default value)
`quiet`	logical; print options after they have been parsed?
`type`	character; one of `have_datum_files`, `proj`, `ellps`, `datum`, `units` or `prime_meridians`; see Details.
`path`	character; PROJ search path to be set

Details

Transforms coordinates of object to new projection. Features that cannot be transformed are returned as empty geometries.

The st_transform method for sfg objects assumes that the CRS of the object is available as an attribute of that name.

For a discussion of using options, see https://github.com/r-spatial/sf/issues/280 and https://github.com/r-spatial/sf/issues/541

sf_proj_info lists the available projections, ellipses, datums, units, or data search path of the PROJ library when type is equal to proj, ellps, datum, units or path; when type equals have_datum_files a boolean is returned indicating whether datum files are installed and accessible (checking for conus).

for PROJ >= 6, sf_proj_info does not provide option type = "datums". PROJ < 6 does not provide the option type = "prime_meridians".

for PROJ >= 7.1.0, the "units" query of sf_proj_info returns the to_meter variable as numeric, previous versions return a character vector containing a numeric expression.

Examples

p1 = st_point(c(7,52))
p2 = st_point(c(-30,20))
sfc = st_sfc(p1, p2, crs = 4326)
sfc
st_transform(sfc, 3857)
st_transform(st_sf(a=2:1, geom=sfc), "+init=epsg:3857")
try(st_transform(sfc, 3857, aoi = c(-280,-90,180,90)))
if (sf_extSoftVersion()["GDAL"] >= "3.0.0") {
  st_transform(sfc, pipeline =
	  "+proj=pipeline +step +proj=axisswap +order=2,1") # reverse axes
  st_transform(sfc, pipeline =
	  "+proj=pipeline +step +proj=axisswap +order=2,1", reverse = TRUE) # also reverse axes
}
nc = st_read(system.file("shape/nc.shp", package="sf"))
st_area(nc[1,]) # area from long/lat
st_area(st_transform(nc[1,], 32119)) # NC state plane, m
st_area(st_transform(nc[1,], 2264)) # NC state plane, US foot
library(units)
set_units(st_area(st_transform(nc[1,], 2264)), m^2)
st_transform(structure(p1, proj4string = "+init=epsg:4326"), "+init=epsg:3857")
st_wrap_dateline(st_sfc(st_linestring(rbind(c(-179,0),c(179,0))), crs = 4326))
library(maps)
wrld <- st_as_sf(maps::map("world", fill = TRUE, plot = FALSE))
wrld_wrap <- st_wrap_dateline(wrld, options = c("WRAPDATELINE=YES", "DATELINEOFFSET=180"),
   quiet = TRUE)
wrld_moll <- st_transform(wrld_wrap, "+proj=moll")
plot(st_geometry(wrld_moll), col = "transparent")
sf_proj_info("datum")

sf

Simple Features for R

v0.9-8

GPL-2 | MIT + file LICENSE

Authors

Edzer Pebesma [aut, cre] (<https://orcid.org/0000-0001-8049-7069>), Roger Bivand [ctb] (<https://orcid.org/0000-0003-2392-6140>), Etienne Racine [ctb], Michael Sumner [ctb], Ian Cook [ctb], Tim Keitt [ctb], Robin Lovelace [ctb], Hadley Wickham [ctb], Jeroen Ooms [ctb] (<https://orcid.org/0000-0002-4035-0289>), Kirill Müller [ctb], Thomas Lin Pedersen [ctb], Dan Baston [ctb]

Initial release