map2SpatialLines and map('world2')

Greetings R-sig-geo'ders;

I want to use the Pacific-centric world map 'world2' from the maps package
for use with hurricane observations. I am also making use of the sp spatial
data classes. The following (Atlantic-centric) example works:

x = map('world', plot=F)
x_sl = map2SpatialLines(x, proj4string=CRS("+proj=longlat +datum=WGS84"))

However, the map2SpatialLines function when using 'world2' - the
Pacific-centric world map - fails.

x_pac = map('world2', plot=F)
x_pac_sl = map2SpatialLines(x, proj4string=CRS("+proj=longlat
+datum=WGS84"))
*Error in validityMethod(object) :
 Geographical CRS given to non-conformant data*

Interestingly: The range on longitude for x is roughly 0 to 180, while the
range on longitude for x_pac is 0 to 360. Didn't know if that had something
to do with it.

x_pac$range

[1]  -5.072266 369.988892 -85.443077  83.573914

x$range

[1] -179.95721  190.29080  -85.44308   83.57391

where the world2 data falls foul of:

sp:::.ll_sanity

function (bb)
{
     tol <- .Machine$double.eps^0.25
     W <- bb[1, 1] < -180 && !isTRUE(all.equal((bb[1, 1] - -180),
         0, tolerance = tol))
     E <- bb[1, 2] > 360 && !isTRUE(all.equal((bb[1, 2] - 360),
         0, tolerance = tol))
     S <- bb[2, 1] < -90 && !isTRUE(all.equal((bb[2, 1] - -90),
         0, tolerance = tol))
     N <- bb[2, 2] > 90 && !isTRUE(all.equal((bb[2, 2] - 90),
         0, tolerance = tol))
     return(!(any(W || E || S || N)))
}
<environment: namespace:sp>

and its limit at just over 360 degrees. If what you need are lines as a 
background, then pruneMap() may help:

x_pac_sl = map2SpatialLines(pruneMap(x_pac, xlim=c(0, 360)),
   proj4string=CRS("+proj=longlat +datum=WGS84"))

by trimming lines. Alternatives through recenter methods often lead to 
horizonal stripes.

Hope this helps,

Roger

Thanks in advance,

- Rob Hodges
FSU, Geography

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Roger Bivand
Department of Economics, NHH Norwegian School of Economics,
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