sf (version 0.9-4)

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 sfc
st_transform(
  x,
  crs = st_crs(x),
  ...,
  aoi = numeric(0),
  pipeline = character(0),
  reverse = FALSE,
  partial = TRUE,
  check = FALSE
)
# S3 method for sf
st_transform(x, crs = st_crs(x), ...)
# S3 method for sfg
st_transform(x, crs = st_crs(x), ...)
sf_proj_info(type = "proj", path)
st_wrap_dateline(x, options, quiet)
# S3 method for sfc
st_wrap_dateline(x, options = "WRAPDATELINE=YES", quiet = TRUE)
# S3 method for sf
st_wrap_dateline(x, options = "WRAPDATELINE=YES", quiet = TRUE)
# S3 method for sfg
st_wrap_dateline(x, options = "WRAPDATELINE=YES", quiet = TRUE)

Arguments

x

object of class sf, sfc or sfg

crs

coordinate reference system: integer with the EPSG code, or character with proj4string

...

ignored

aoi

area of interest, in degrees: WestLongitude, SouthLatitude, EastLongitude, NorthLatitude

pipeline

character; proj4 or WKT coordinate operation, to override the default operation

reverse

boolean; if TRUE, the inverse operation of the pipeline is applied

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; perform a sanity check on resulting polygons?

type

character; one of have_datum_files, proj, ellps, datum, units or prime_meridians; see Details.

path

character; PROJ search path to be set

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?

Details

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

Projecting to projections not supported by GDAL may be done by st_transform_proj, part of package lwgeom.

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

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).

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

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

Examples

# NOT RUN {
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")
sf_proj_info("datum")
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")
# }

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