Read a GAL lattice file into a neighbours list

The function read.gal() reads a GAL lattice file into a neighbours list for spatial analysis. It will read old and new style (GeoDa) GAL files. The function read.geoda is a helper file for reading comma separated value data files, calling read.csv().

Usage

read.gal(file, region.id=NULL, override.id=FALSE)
read.geoda(file, row.names=NULL, skip=0)

Arguments

file: name of file with GAL lattice data
region.id: region IDs in specified order to coerse neighbours list order and numbering to that of the region.id
override.id: override any given (or NULL) region.id, collecting region.id numbering and order from the GAL file.
row.names: as in row.names in read.csv(), typically a character string naming the column of the file to be used
skip: skip number of lines, as in read.csv()

Details

Luc Anselin (2003): Spatial Analysis Laboratory, Department of Agricultural and Consumer Economics, University of Illinois, Urbana-Champaign, now dead link: http://www.csiss.org/gispopsci/workshops/2011/PSU/readings/W15_Anselin2007.pdf; Luc Anselin (2003) GeoDa 0.9 User's Guide, pp. 80–81, Spatial Analysis Laboratory, Department of Agricultural and Consumer Economics, University of Illinois, Urbana-Champaign, http://geodacenter.github.io/docs/geoda093.pdf; GAL - Geographical Algorithms Library, University of Newcastle

Value

The function read.gal() returns an object of class nb with a list of integer vectors containing neighbour region number ids. The function read.geoda returns a data frame, and issues a warning if the returned object has only one column.

Author

Roger Bivand Roger.Bivand@nhh.no

Note

Example data originally downloaded from now dead link: http://sal.agecon.uiuc.edu/weights/zips/us48.zip

Examples

us48.fipsno <- read.geoda(system.file("etc/weights/us48.txt",
 package="spdep")[1])
us48.q <- read.gal(system.file("etc/weights/us48_q.GAL", package="spdep")[1],
 us48.fipsno$Fipsno)
us48.r <- read.gal(system.file("etc/weights/us48_rk.GAL", package="spdep")[1],
 us48.fipsno$Fipsno)
data(state)
if (as.numeric(paste(version$major, version$minor, sep="")) < 19) {
 m50.48 <- match(us48.fipsno$"State.name", state.name)
} else {
 m50.48 <- match(us48.fipsno$"State_name", state.name)
}
plot(us48.q, as.matrix(as.data.frame(state.center))[m50.48,])
plot(diffnb(us48.r, us48.q),
 as.matrix(as.data.frame(state.center))[m50.48,], add=TRUE, col="red")
#> Warning: neighbour object has 46 sub-graphs
title(main="Differences between rook and queen criteria imported neighbours lists")