refocusWorld function

Refocus the worldLL/worldLLhigh Data Sets

Refocus the worldLL/worldLLhigh data sets, e.g., refocus them so that Eastern Canada appears to the west of Western Europe.

refocusWorld (polys, xlim=NULL, ylim=NULL, clip.AN=TRUE)

Arguments

• polys: PolySet -- object with one or more polygons; typically worldLL or worldLLhigh (required).
• xlim: numeric -- range of X-coordinates.
• ylim: numeric -- range of Y-coordinates.
• clip.AN: logical -- if TRUE, clip expanded Antarctica to 'xlim' of refocused polygons other than Antarctica and to user-defined/default 'ylim'.

Details

This function accepts a PolySet containing one or more polygons with X-coordinates that collectively span approximately 360 degrees. The function effectively joins the PolySet into a cylinder and then splits it at an arbitrary longitude according to the user-specified limits. Modifications in the resulting PolySet

are restricted to shifting X-coordinates by +/- multiples of 360 degrees, and instead of clipping polygons, the return value simply omits out-of-range polygons.

Returns

PolySet , likely a subset of the input PolySet , which retains the same PID/SID values.

Author(s)

Nicholas M. Boers, Staff Software Engineer

Jobber, Edmonton AB

Rowan Haigh, Program Head -- Offshore Rockfish

Pacific Biological Station (PBS), Fisheries & Oceans Canada (DFO), Nanaimo BC

locus opus: Institute of Ocean Sciences (IOS), Sidney BC

Last modified Rd: 2018-10-26

Note

The Antarctic polygon is treated as a special case in that it is expanded longitudinally by duplicating it to the West and East of the base polygon. The expanded Antarctica is then clipped to the limits of the plot, or not if 'clip.NA=FALSE'.

See Also

joinPolys

Examples

local(envir=.PBSmapEnv,expr={
  oldpar = par(no.readonly=TRUE)
  #--- load appropriate data
  data(worldLL,envir=.PBSmapEnv)
  #--- set limits
  xlim <- c(-100,25)
  ylim <- c(0,90)
  #--- refocus and plot the world
  polys <- refocusWorld(worldLL, xlim, ylim)
  plotMap(polys, xlim, ylim)
  par(oldpar)
})