1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
|
\name{readShapePoly}
\alias{readShapePoly}
\alias{writePolyShape}
%- Also NEED an '\alias' for EACH other topic documented here.
\title{Read polygon shape files into SpatialPolygonsDataFrame objects}
\description{
The \code{readShapePoly} reads data from a polygon shapefile into a \code{SpatialPolygonsDataFrame} object. The \code{writePolyShape} function writes data from a \code{SpatialPolygonsDataFrame} object to a shapefile. Note DBF file restrictions in \code{\link[foreign]{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)
}
%- maybe also 'usage' for other objects documented here.
\arguments{
\item{fn}{shapefile layer name, when writing omitting the extensions *.shp, *.shx and *.dbf, which are added in the function}
\item{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}
\item{proj4string}{Object of class \code{CRS}; holding a valid proj4 string}
\item{verbose}{default TRUE - report type of shapefile and number of shapes}
\item{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.}
\item{force_ring}{if TRUE, close unclosed input rings}
\item{delete_null_obj}{if TRUE, null geometries will be removed together with their data.frame rows}
\item{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}
\item{x}{a \code{SpatialPolygonsDataFrame} object}
\item{factor2char}{logical, default TRUE, convert factor columns to character}
\item{max_nchar}{default 254, may be set to a higher limit and passed through to the DBF writer, please see Details in \code{\link[foreign]{write.dbf}}}
}
\details{If no IDvar argument is given, the shpID values of the shapefile will be used as \code{Polygons} ID values; when writing shapefiles, the object data slot row.names are added to the DBF file as column SP\_ID.}
\value{
a SpatialPolygonsDataFrame object
}
\author{ Roger Bivand }
\seealso{\code{\link[foreign]{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=""))
}
\keyword{spatial}
|
