maptools (version 1.1-4)

readShapePoly: Read polygon shape files into SpatialPolygonsDataFrame objects

Description

The use of this function is deprecated and it is not being maintained. Use rgdal::readOGR() or sf::st_read() instead - both of these read the coordinate reference system from the input file, while this deprecated function does not.For writing, use rgdal::writeOGR() or sf::st_write() instead.

The readShapePoly reads data from a polygon shapefile into a SpatialPolygonsDataFrame object. The writePolyShape function writes data from a SpatialPolygonsDataFrame object to a shapefile. Note DBF file restrictions in write.dbf.

Usage

readShapePoly(fn, IDvar=NULL, proj4string=CRS(as.character(NA)),
 verbose=FALSE, repair=FALSE, force_ring=FALSE, delete_null_obj=FALSE,
 retrieve_ABS_null=FALSE)
writePolyShape(x, fn, factor2char = TRUE, max_nchar=254)

Value

a SpatialPolygonsDataFrame object

Arguments

fn

shapefile layer name, when writing omitting the extensions *.shp, *.shx and *.dbf, which are added in the function

IDvar

a character string: the name of a column in the shapefile DBF containing the ID values of the shapes - the values will be converted to a character vector

proj4string

Object of class CRS; holding a valid proj4 string

verbose

default FALSE - report type of shapefile and number of shapes

repair

default FALSE: some shapefiles provided by Geolytics Inc. have values of object sizes stored in the *.shx index file that are eight bytes too large, leading the function to try to read past the end of file. If repair=TRUE, an attempt is made to repair the internal values, permitting such files to be read.

force_ring

if TRUE, close unclosed input rings

delete_null_obj

if TRUE, null geometries will be removed together with their data.frame rows

retrieve_ABS_null

default FALSE, if TRUE and delete_null_obj also TRUE, the function will return a data frame containing the data from any null geometries inserted by ABS

x

a SpatialPolygonsDataFrame object

factor2char

logical, default TRUE, convert factor columns to character

max_nchar

default 254, may be set to a higher limit and passed through to the DBF writer, please see Details in write.dbf

Author

Roger Bivand

Details

If no IDvar argument is given, the shpID values of the shapefile will be used as Polygons ID values; when writing shapefiles, the object data slot row.names are added to the DBF file as column SP_ID.

See Also

write.dbf

Examples

library(maptools)
xx <- readShapePoly(system.file("shapes/sids.shp", package="maptools")[1],
 IDvar="FIPSNO", proj4string=CRS("+proj=longlat +ellps=clrk66"))
plot(xx, border="blue", axes=TRUE, las=1)
text(coordinates(xx), labels=row.names(xx), cex=0.6)
as(xx, "data.frame")[1:5, 1:6]
xxx <- xx[xx$SID74 < 2,]
plot(xxx, border="red", add=TRUE)
tmpfl <- paste(tempdir(), "xxpoly", sep="/")
writePolyShape(xxx, tmpfl)
getinfo.shape(paste(tmpfl, ".shp", sep=""))
axx <- readShapePoly(tmpfl, proj4string=CRS("+proj=longlat +ellps=clrk66"))
plot(xxx, border="black", lwd=4)
plot(axx, border="yellow", lwd=1, add=TRUE)
unlink(paste(tmpfl, ".*", sep=""))