subset.listw: Subset a spatial weights list

In spdep: Spatial Dependence: Weighting Schemes, Statistics and Models

Description

The function subsets a spatial weights list, retaining objects for which the subset argument vector is TRUE. At present it will only subset non-general weights lists (that is those created by nb2listw with glist=NULL).

Usage

## S3 method for class 'listw'
subset(x, subset, zero.policy = NULL, ...)

Arguments

x	an object of class listw
subset	logical expression
zero.policy	default NULL, use global option value; if FALSE stop with error for any empty neighbour sets, if TRUE permit the weights list to be formed with zero-length weights vectors - passed through to nb2listw
...	generic function pass-through

Value

The function returns an object of class listw with component style the same as the input object, component neighbours a list of integer vectors containing neighbour region number ids (compacted to run from 1:number of regions in subset), and component weights as the weights computed for neighbours using style.

Author(s)

Roger Bivand [e-mail]

See Also

nb2listw, subset.nb

Examples

example(columbus)
to.be.dropped <- c(31, 34, 36, 39, 42, 46)
pre <- nb2listw(col.gal.nb)
print(pre)
post <- subset(pre, !(1:length(col.gal.nb) %in% to.be.dropped))
print(post)

Example output

Loading required package: sp
Loading required package: Matrix

colmbs> require(maptools)
Loading required package: maptools
Checking rgeos availability: TRUE

colmbs> columbus <- readShapePoly(system.file("etc/shapes/columbus.shp",
colmbs+  package="spdep")[1])

colmbs> col.gal.nb <- read.gal(system.file("etc/weights/columbus.gal",
colmbs+  package="spdep")[1])
Warning message:
use rgdal::readOGR or sf::st_read 
Characteristics of weights list object:
Neighbour list object:
Number of regions: 49 
Number of nonzero links: 230 
Percentage nonzero weights: 9.579342 
Average number of links: 4.693878 

Weights style: W 
Weights constants summary:
   n   nn S0       S1       S2
W 49 2401 49 23.48489 204.6687
Characteristics of weights list object:
Neighbour list object:
Number of regions: 43 
Number of nonzero links: 212 
Percentage nonzero weights: 11.46566 
Average number of links: 4.930233 

Weights style: W 
Weights constants summary:
   n   nn S0       S1       S2
W 43 1849 43 19.26584 178.4604

spdep documentation built on Aug. 19, 2017, 3:01 a.m.