spdep (version 0.5-82)

nb2lines: Use arc-type shapefiles for import and export of weights

Description

Use arc-type shapefiles for import and export of weights, storing spatial entity coordinates in the arcs, and the entity indices in the data frame.

Usage

nb2lines(nb, wts, coords, proj4string=CRS(as.character(NA)))
listw2lines(listw, coords, proj4string=CRS(as.character(NA)))
df2sn(df, i="i", i_ID="i_ID", j="j", wt="wt")

Arguments

nb

a neighbour object of class nb

wts

list of general weights corresponding to neighbours

coords

matrix of region point coordinates

proj4string

Object of class CRS; holding a valid proj4 string

listw

a listw object of spatial weights

df

a data frame read from a shapefile, derived from the output of nb2lines

i

character name of column in df with from entity index

i_ID

character name of column in df with from entity region ID

j

character name of column in df with to entity index

wt

character name of column in df with weights

Value

• nb2lines and listw2lines return a SpatialLinesDataFrame object; its data slot contains a data frame with the from and to indices of the neighbour links and their weights. df2sn converts the data retrieved from reading the data from df back into a spatial.neighbour object.

Details

The maptools package function writeSpatialShape is used to transport out the list of lines made by nb2lines or listw2lines, which is a simple wrapper function. The neighbour and weights objects may be retrieved by converting the specified columns of the data slot of the SpatialLinesDataFrame object into a spatial.neighbour object, which is then converted into a weights list object.

See Also

sn2listw, readShapeLines

Examples

require(maptools)
example(columbus)
coords <- coordinates(columbus)
res <- listw2lines(nb2listw(col.gal.nb), coords)
summary(res)
fn <- paste(tempdir(), "nbshape", sep="/")
writeLinesShape(res, fn=fn)
inMap <- readShapeLines(fn)
summary(inMap)
diffnb(sn2listw(df2sn(as(inMap, "data.frame")))$neighbours, col.gal.nb)