spdep (version 1.2-4)

read.gal: Read a GAL lattice file into a neighbours list

Description

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)

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.

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()

Author

Roger Bivand

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

See Also

summary.nb

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")
title(main="Differences between rook and queen criteria imported neighbours lists")