Read polygon shape files into SpatialPolygonsDataFrame objects
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.
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)
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 |
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 |
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 |
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.
a SpatialPolygonsDataFrame object
Roger Bivand
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=""))Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.