refocusWorld: Refocus the 'worldLL'/'worldLLhigh' Data Sets

In PBSmapping: Mapping Fisheries Data and Spatial Analysis Tools

Refocus the worldLL/worldLLhigh Data Sets

Description

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

Usage

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.

Value

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

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'.

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

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)
})

PBSmapping documentation built on Sept. 30, 2024, 9:21 a.m.