# nowrapRecenter

0th

Percentile

##### Break polygons at meridian for recentering

When recentering a world map, say to change an "Atlantic" view with longitude range -180 to 180, to a "Pacific" view, with longitude range 0 to 360, polygons crossed by the new offset, here 0/360, need to be clipped into left and right sub.polygons to avoid horizontal scratches across the map. The nowrapSpatialPolygons function performs this operation using polygon intersection, and nowrapRecenter recenters the output SpatialPolygons object.

Keywords
spatial
##### Usage
nowrapRecenter(obj, offset = 0, eps = rep(.Machine$double.eps, 2)) nowrapSpatialPolygons(obj, offset = 0, eps=rep(.Machine$double.eps, 2))
##### Arguments
obj
A SpatialPolygons object
offset
offset from the Greenwich meridian
eps
vector of two (left and right) fuzz factors to retract the ring from the offset
##### Value

• A SpatialPolygons object

recenter, nowrapSpatialLines

##### Aliases
• nowrapRecenter
• nowrapSpatialPolygons
##### Examples
library(gpclib)
library(maps)
world <- map("world", fill=TRUE, col="transparent", plot=FALSE)
worldSpP <- map2SpatialPolygons(world, world\$names, CRS("+proj=longlat"))
worldSpPr <- recenter(worldSpP)
plot(worldSpPr)
title("Pacific view without polygon splitting")
worldSpPnr <- nowrapRecenter(worldSpP)
plot(worldSpPnr)
title("Pacific view with polygon splitting")
crds <- matrix(c(-1, 1, 1, -1, 50, 50, 52, 52), ncol=2)
rcrds <- rbind(crds, crds[1,])
SR <- SpatialPolygons(list(Polygons(list(Polygon(rcrds)), ID="r1")), proj4string=CRS("+proj=longlat"))
bbox(SR)
SRr <- recenter(SR)
bbox(SRr)
SRnr <- nowrapRecenter(SR)
bbox(SRnr)
Documentation reproduced from package maptools, version 0.6-3, License: GPL version 2 or later (R and interface code), MIT (shapelib code)

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