R: Subset a spatial weights list

subset.listw {spdep} | R Documentation

## Subset a spatial weights list

### 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 Roger.Bivand@nhh.no

### See Also

`nb2listw`, `subset.nb`

### Examples

    col.gal.nb <- read.gal(system.file("weights/columbus.gal", package="spData")[1])
    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)

[Package spdep version 1.2-2 Index]