sf (version 0.6-0)

st_read: Read simple features or layers from file or database


Read simple features from file or database, or retrieve layer names and their geometry type(s)

Read PostGIS table directly through DBI and RPostgreSQL interface, converting binary


st_read(dsn, layer, ...)

# S3 method for default st_read(dsn, layer, ..., options = NULL, quiet = FALSE, geometry_column = 1L, type = 0, promote_to_multi = TRUE, stringsAsFactors = default.stringsAsFactors(), int64_as_string = FALSE, check_ring_dir = FALSE)

read_sf(..., quiet = TRUE, stringsAsFactors = FALSE)

st_read_db(conn = NULL, table = NULL, query = NULL, geom_column = NULL, EWKB, ...)



data source name (interpretation varies by driver - for some drivers, dsn is a file name, but may also be a folder, or contain the name and access credentials of a database); in case of GeoJSON, dsn may be the character string holding the geojson data


layer name (varies by driver, may be a file name without extension); in case layer is missing, st_read will read the first layer of dsn, give a warning and (unless quiet = TRUE) print a message when there are multiple layers, or give an error if there are no layers in dsn.


parameter(s) passed on to st_as_sf


character; driver dependent dataset open options, multiple options supported.


logical; suppress info on name, driver, size and spatial reference, or signaling no or multiple layers


integer or character; in case of multiple geometry fields, which one to take?


integer; ISO number of desired simple feature type; see details. If left zero, and promote_to_multi is TRUE, in case of mixed feature geometry types, conversion to the highest numeric type value found will be attempted. A vector with different values for each geometry column can be given.


logical; in case of a mix of Point and MultiPoint, or of LineString and MultiLineString, or of Polygon and MultiPolygon, convert all to the Multi variety; defaults to TRUE


logical; logical: should character vectors be converted to factors? The `factory-fresh' default is TRUE, but this can be changed by setting options(stringsAsFactors = FALSE).


logical; if TRUE, Int64 attributes are returned as string; if FALSE, they are returned as double and a warning is given when precision is lost (i.e., values are larger than 2^53).


logical; if TRUE, polygon ring directions are checked and if necessary corrected (when seen from above: exterior ring counter clockwise, holes clockwise)


open database connection


table name


SQL query to select records; see details


character or integer: indicator of name or position of the geometry column; if not provided, the last column of type character is chosen


logical; is the WKB is of type EWKB? if missing, defaults to TRUE if conn is of class codePostgreSQLConnection or PqConnection, and to FALSE otherwise


object of class sf when a layer was successfully read; in case argument layer is missing and data source dsn does not contain a single layer, an object of class sf_layers is returned with the layer names, each with their geometry type(s). Note that the number of layers may also be zero.


for geometry_column, see also https://trac.osgeo.org/gdal/wiki/rfc41_multiple_geometry_fields; for type values see https://en.wikipedia.org/wiki/Well-known_text#Well-known_binary, but note that not every target value may lead to successful conversion. The typical conversion from POLYGON (3) to MULTIPOLYGON (6) should work; the other way around (type=3), secondary rings from MULTIPOLYGONS may be dropped without warnings. promote_to_multi is handled on a per-geometry column basis; type may be specified for each geometry column.

In case of problems reading shapefiles from USB drives on OSX, please see https://github.com/r-spatial/sf/issues/252.

read_sf and write_sf are aliases for st_read and st_write, respectively, with some modified default arguments. read_sf and write_sf are quiet by default: they do not print information about the data source. write_sf delete layers by default: it overwrites existing files.

if table is not given but query is, the spatial reference system (crs) of the table queried is only available in case it has been stored into each geometry record (e.g., by PostGIS, when using EWKB)

in case geom_column is missing: if table is missing, this function will try to read the name of the geometry column from table geometry_columns, in other cases, or when this fails, the geom_column is assumed to be the last column of mode character. If table is missing, the SRID cannot be read and resolved into a proj4string by the database, and a warning will be given.


Run this code
nc = st_read(system.file("shape/nc.shp", package="sf"))
summary(nc) # note that AREA was computed using Euclidian area on lon/lat degrees

# }
  example(meuse, ask = FALSE, echo = FALSE)
  try(st_write(st_as_sf(meuse), "PG:dbname=postgis", "meuse",
       layer_options = "OVERWRITE=true"))
  try(st_meuse <- st_read("PG:dbname=postgis", "meuse"))
  if (exists("st_meuse"))
# }
# read geojson from string:
geojson_txt <- paste("{\"type\":\"MultiPoint\",\"coordinates\":",
x = read_sf(geojson_txt)
# }
try(conn <- dbConnect(PostgreSQL(), dbname = "postgis"))
if (exists("conn") && !inherits(conn, "try-error")) {
  x = st_read_db(conn, "meuse", query = "select * from meuse limit 3;")
  x = st_read_db(conn, table = "public.meuse")
  print(st_crs(x)) # SRID resolved by the database, not by GDAL!
# }

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