R: Split SpatialLines components at offset

nowrapSpatialLines {maptools} | R Documentation

## Split SpatialLines components at offset

### Description

When recentering a world map, most often from the "Atlantic" view with longitudes with range -180 to 180, to the "pacific" view with longitudes with range 0 to 360, lines crossing the offset (0 for this conversion) get stretched horizonally. This function breaks Line objects at the offset (usually Greenwich), inserting a very small gap, and reassembling the Line objects created as Lines. The rgeos package is required to use this function.

### Usage

    nowrapSpatialLines(obj, offset = 0, eps = rep(.Machine$double.eps^(1/2.5), 2))

### Arguments

`obj` | A Spatial Lines object
`offset` | default 0, untried for other values
`eps` | vector of two fuzz values, both default 2.5 root of double.eps

### Value

A Spatial Lines object

### Author(s)

Roger Bivand

### See Also

`recenter-methods`, `nowrapSpatialPolygons`

### Examples

    Sl <- SpatialLines(list(Lines(list(Line(cbind(sin(seq(-4,4,0.4)),
     seq(1,21,1)))), "1")), proj4string=CRS("+proj=longlat +ellps=WGS84"))
    summary(Sl)
    if (require(rgeos)) {
    nwSL <- nowrapSpatialLines(Sl)
    summary(nwSL)
    if(require(maps)) {
    worldmap <- map("world", plot=FALSE)
    worldmapLines <- map2SpatialLines(worldmap, proj4string=CRS("+proj=longlat +datum=WGS84"))
    bbox(worldmapLines)
    t0 <- nowrapSpatialLines(worldmapLines, offset=180)
    bbox(t0)
    }
    }

[Package maptools version 0.9-3 Index]