read.gal {spdep} | R Documentation

## 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)

### 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, http://sal.agecon.uiuc.edu/weights/howto.html; 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://agec221.agecon.uiuc.edu/csiss/pdf/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.

### Note

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

### Author(s)

Roger Bivand Roger.Bivand@nhh.no

### 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")

[Package spdep version 0.3-25 Index]