readOGR {rgdal}R Documentation

Read OGR vector maps into Spatial objects

Description

The function reads an OGR data source and layer into a suitable Spatial vector object. It can only handle layers with conformable geometry features (not mixtures of points, lines, or polygons in a single layer). It will set the spatial reference system if the layer has such metadata.

Usage

readOGR(dsn, layer, verbose = TRUE, p4s=NULL, drop_unsupported_fields=FALSE,
 input_field_name_encoding=NULL)
ogrInfo(dsn, layer, input_field_name_encoding=NULL)
ogrFIDs(dsn, layer)
ogrDrivers()
## S3 method for class 'ogrinfo':
print(x, ...)

Arguments

dsn data source name (interpretation varies by driver — for some drivers, dsn is a file name, but may also be a folder)
layer layer name (varies by driver, may be a file name without extension)
verbose report progress
p4s PROJ4 string defining CRS, if default NULL, the value is read from the OGR data set
drop_unsupported_fields default FALSE, if TRUE skip fields other than string, integer, and real
input_field_name_encoding default NULL; if not NULL, should be a valid encoding name for the source platform of the data source and layer, see iconv
x ogrinfo object
... other arguments to print method

Details

The drivers available will depend on the installation of GDAL/OGR, and can vary; the ogrDrivers() function shows which are available, and which may be written (but all are assumed to be readable). Note that stray files in data source directories (such as *.dbf) may lead to suprious errors that accompanying *.shp are missing.

Value

A Spatial object is returned suiting the vector data source, either a SpatialPointsDataFrame (using an AttributeList for its data slot directly), a SpatialLinesDataFrame, or a SpatialPolygonsDataFrame.

Note

The bases for this implementation are taken from functions in Barry Rowlingson's draft Rmap package, and from Radim Blazek's v.in.ogr program in GRASS.

Please note that the OGR drivers used may not handle missing data gracefully, and be prepared to have to correct for this manually. From rgdal 0.5-27, missing value handling has been improved, and OGR unset field values are set to NA in R, but drivers and external files may vary in their representations of missing values.

Author(s)

Roger Bivand

References

http://www.gdal.org/ogr/, http://www.gdal.org/ogr/ogr_formats.html, http://examples.oreilly.com/webmapping/

See Also

SpatialPointsDataFrame-class, SpatialLinesDataFrame-class, SpatialPolygonsDataFrame-class, readShapePoly, iconv

Examples

ogrDrivers()
ogrInfo(system.file("vectors", package = "rgdal")[1], "cities")
cities <- readOGR(system.file("vectors", package = "rgdal")[1], "cities")
summary(cities)
ogrInfo(system.file("vectors", package = "rgdal")[1], "kiritimati_primary_roads")
kiritimati_primary_roads <- readOGR(system.file("vectors", package = "rgdal")[1], "kiritimati_primary_roads")
summary(kiritimati_primary_roads)
ogrInfo(system.file("vectors", package = "rgdal")[1], "scot_BNG")
scot_BNG <- readOGR(system.file("vectors", package = "rgdal")[1], "scot_BNG")
summary(scot_BNG)
if ("GML" %in% ogrDrivers()$name) {
  airports <- try(readOGR(system.file("vectors/airports.gml", package = "rgdal")[1], "airports"))
  if (class(airports) != "try-error") summary(airports)
}
ogrInfo(system.file("vectors/ps_cant_31.MIF", package = "rgdal")[1], "ps_cant_31")
ps_cant_31 <- readOGR(system.file("vectors/ps_cant_31.MIF", package = "rgdal")[1], "ps_cant_31")
summary(ps_cant_31)
ogrInfo(system.file("vectors/Up.tab", package = "rgdal")[1], "Up")
Up <- readOGR(system.file("vectors/Up.tab", package = "rgdal")[1], "Up")
summary(Up)

[Package rgdal version 0.6-7 Index]