| readShapePoly {maptools} | R Documentation |
The readShapePoly reads data from a polygon shapefile into a SpatialPolygonsDataFrame object. The writePolyShape function writes data from a SpatialPolygonsDataFrame object to a shapefile.
readShapePoly(fn, IDvar=NULL, proj4string=CRS(as.character(NA)), verbose=FALSE, repair=FALSE, force_ring=FALSE) writePolyShape(x, fn, factor2char = TRUE)
fn |
shapefile layer name, without extension |
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 TRUE - 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 |
x |
a SpatialPolygonsDataFrame object |
factor2char |
logical, default TRUE, convert factor columns to character |
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 rownames 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(getSpPPolygonsLabptSlots(xx), labels=getSpPPolygonsIDSlots(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(), "xxline", 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=""))