rgdal (version 1.1-10)

readOGR: 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.

If reading a shapefile, the data source name (dsn= argument) is the folder (directory) where the shapefile is, and the layer is the name of the shapefile (without the .shp extension). For example to read bounds.shp from C:/Maps, do map <- readOGR(dsn="C:/Maps", layer="bounds"). The logic behind this is that typically one keeps all the shapefiles for a project in one folder (directory).

As noted below, for other file type drivers, the dsn= argument is interpreted differently, and may be the file name itself, as for example with the GPX driver for reading GPS data as layer="tracks" lines or layer="track_points" points.

Usage

readOGR(dsn, layer, verbose = TRUE, p4s=NULL,  stringsAsFactors=default.stringsAsFactors(),  drop_unsupported_fields=FALSE, pointDropZ=FALSE, dropNULLGeometries=TRUE, useC=TRUE, disambiguateFIDs=FALSE, addCommentsToPolygons=TRUE, encoding=NULL, use_iconv=FALSE, swapAxisOrder=FALSE, require_geomType = NULL, integer64="allow.loss")
ogrInfo(dsn, layer, encoding=NULL, use_iconv=FALSE, swapAxisOrder=FALSE, require_geomType = NULL)
ogrFIDs(dsn, layer)
ogrDrivers()
OGRSpatialRef(dsn, layer)
ogrListLayers(dsn)
"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

stringsAsFactors

logical: should character vectors be converted to factors? The ‘factory-fresh’ default is TRUE, but this can be changed by setting options(stringsAsFactors = FALSE) (see link[base]{data.frame}).

drop\_unsupported\_fields

default FALSE, if TRUE skip fields other than String, Integer, and Real; Date, Time and DateTime are converted to String

pointDropZ

default FALSE, if TRUE, discard third coordinates for point geometries; third coordinates are alway discarded for line and polygon geometries

dropNULLGeometries

default TRUE, drop both declared NULL geometries, and empty geometries with no coordinates; if FALSE, return a data frame with the attribute values of the NULL and empty geometries

useC

default TRUE, if FALSE use original interpreted code in a loop

disambiguateFIDs

default FALSE, if TRUE, and FID values are not unique, they will be set to unique values 1:N for N features; problem observed in GML files

addCommentsToPolygons

default TRUE, may be set FALSE for legacy behaviour; used to indicate which interior rings are holes in which exterior rings in conformance with OGC SFS specifications

encoding

default NULL, if set to a character string, and the driver is “ESRI Shapefile”, and use_iconv is FALSE, it is passed to the CPL Option “SHAPE_ENCODING” immediately before reading the DBF of a shapefile. If use_iconv is TRUE, and encoding is not NULL, it will be used to convert input strings from the given value to the native encoding for the system/platform.

use_iconv

default FALSE; if TRUE and encoding is not NULL, it will be used to convert input strings from the given value to the native encoding for the system/platform.

swapAxisOrder

default FALSE, if TRUE, treat y coordinate as Easting, x as Northing, that is the opposite to the assumed order; this may be needed if some OGR read drivers do not behave as expected

require_geomType

, default NULL, if one of: c("wkbPoint", "wkbLineString", "wkbPolygon"), then in input with multiple geometry types, the chosen type will be read

integer64

From GDAL 2, fields to be read may also take Integer64 values. As R has no such storage mode, three options are offered, analogous with type.convert for numeric conversion: “allow.loss” which clamps to 32-bit signed integer, “warn.loss” - as “allow.loss” but warns when clamping occurs, and “no.loss”, which reads as a character string using the formatting applied by default by GDAL. The use of 64-bit integers is usually a misunderstanding, as such data is almost always a long key ID.

x

ogrinfo object

...

other arguments to print method

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.

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.

References

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

See Also

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

Examples

ogrDrivers()
dsn <- system.file("vectors", package = "rgdal")[1]
ogrListLayers(dsn)
ogrInfo(dsn=dsn, layer="cities")
owd <- getwd()
setwd(dsn)
ogrInfo(dsn="cities.shp", layer="cities")
setwd(owd)
cities <- readOGR(dsn=dsn, layer="cities")
summary(cities)
table(Encoding(as.character(cities$NAME)))
ogrInfo(dsn=dsn, layer="kiritimati_primary_roads")
OGRSpatialRef(dsn=dsn, layer="kiritimati_primary_roads")
kiritimati_primary_roads <- readOGR(dsn=dsn, layer="kiritimati_primary_roads")
summary(kiritimati_primary_roads)
ogrInfo(dsn=dsn, layer="scot_BNG")
OGRSpatialRef(dsn=dsn, layer="scot_BNG")
scot_BNG <- readOGR(dsn=dsn, layer="scot_BNG")
summary(scot_BNG)
if ("GML" %in% ogrDrivers()$name) {
  dsn <- system.file("vectors/airports.gml", package = "rgdal")[1]
  airports <- try(readOGR(dsn=dsn, layer="airports"))
  if (class(airports) != "try-error") summary(airports)
}
dsn <- system.file("vectors/ps_cant_31.MIF", package = "rgdal")[1]
ogrInfo(dsn=dsn, layer="ps_cant_31")
ps_cant_31 <- readOGR(dsn=dsn, layer="ps_cant_31")
summary(ps_cant_31)
sapply(as(ps_cant_31, "data.frame"), class)
ps_cant_31 <- readOGR(dsn=dsn, layer="ps_cant_31", stringsAsFactors=FALSE)
summary(ps_cant_31)
sapply(as(ps_cant_31, "data.frame"), class)
dsn <- system.file("vectors/Up.tab", package = "rgdal")[1]
ogrInfo(dsn=dsn, layer="Up")
Up <- readOGR(dsn=dsn, layer="Up")
summary(Up)
dsn <- system.file("vectors/test_trk2.gpx", package = "rgdal")[1]
test_trk2 <- try(readOGR(dsn=dsn, layer="tracks"))
if (class(test_trk2) != "try-error") summary(test_trk2)
test_trk2pts <- try(readOGR(dsn=dsn, layer="track_points"))
if (class(test_trk2pts) != "try-error") summary(test_trk2pts)
dsn <- system.file("vectors", package = "rgdal")[1]
ogrInfo(dsn=dsn, layer="trin_inca_pl03")
birds <- readOGR(dsn=dsn, layer="trin_inca_pl03")
summary(birds)
dsn <- system.file("vectors/PacoursIKA2.TAB", package = "rgdal")[1]
try(ogrInfo(dsn, "PacoursIKA2"))
ogrInfo(dsn, "PacoursIKA2", require_geomType="wkbPoint")
plot(readOGR(dsn, "PacoursIKA2", require_geomType="wkbLineString"), col="red")
plot(readOGR(dsn, "PacoursIKA2", require_geomType="wkbPoint"), add=TRUE)
odir <- getwd()
setwd(system.file("vectors", package = "rgdal")[1])
ow <- options("warn")$warn
options("warn"=1)
ogrInfo("test64.vrt", "test64")
str(readOGR("test64.vrt", "test64", verbose=FALSE, integer64="allow.loss")$val)
str(readOGR("test64.vrt", "test64", verbose=FALSE, integer64="warn.loss")$val)
str(readOGR("test64.vrt", "test64", verbose=FALSE, integer64="no.loss")$val)
str(readOGR("test64.vrt", "test64", verbose=FALSE, stringsAsFactors=FALSE,
 integer64="no.loss")$val)
options("warn"=ow)
setwd(odir)