Making SpatialPolygons objects from RArcInfo input

This function is used in making SpatialPolygons objects from RArcInfo input.

pal2SpatialPolygons(arc, pal, IDs, dropPoly1=TRUE,
 proj4string=CRS(as.character(NA)))

Arguments

IDs

Unique character ID values for each output Polygons object; the input IDs can be an integer or character vector with duplicates, where the duplicates will be combined as a single output Polygons object

proj4string

Object of class "CRS"; holding a valid proj4 string

arc

Object returned by get.arcdata

pal

Object returned by get.paldata

dropPoly1

Should the first polygon in the AVC or e00 data be dropped; the first polygon is typically the compound boundary of the whole dataset, and can be detected by looking at the relative lengths of the list components in the second component of pal, which are the numbers of arcs making up the boundary of each polygon

Value

The functions return a SpatialPolygons object

Author

Roger Bivand

Examples

nc1 <- readShapePoly(system.file("shapes/sids.shp", package="maptools")[1], ID="FIPS")
#> Warning: shapelib support is provided by GDAL through the sf and terra packages among others
plot(nc1)
text(coordinates(nc1), labels=row.names(nc1), cex=0.6)

if(require(maps)){
ncmap <- map("county", "north carolina", fill=TRUE, col="transparent",
 plot=FALSE)
IDs <- sapply(strsplit(ncmap$names, "[,:]"), function(x) x[2])
nc2 <- map2SpatialPolygons(ncmap, IDs)
plot(nc2)
text(coordinates(nc2), labels=row.names(nc2), cex=0.6)
}

#if(require(RArcInfo)) {
#td <- tempdir()
#tmpcover <- paste(td, "nc", sep="/")
#if (!file.exists(tmpcover)) e00toavc(system.file("share/co37_d90.e00",
# package="maptools")[1], tmpcover)
#arc <- get.arcdata(td, "nc")
#pal <- get.paldata(td, "nc")
#pat <- get.tabledata(paste(td, "info", sep="/"), "NC.PAT")
#sapply(pal[[2]], function(x) length(x[[1]]))
#IDs <- paste(pat$ST[-1], pat$CO[-1], sep="")
#nc3 <- pal2SpatialPolygons(arc, pal, IDs=IDs)
#plot(nc3)
#text(coordinates(nc3), labels=row.names(nc3), cex=0.6)
#}