How to display the map within two longitude lines

Question

I am new to GIS and I try to use the following code to display a pacific-centered world map.

+proj=robin +lon_0=-198 +x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs

However the map displayed is a bit messy as below:

I'm wondering whether I can limit the map within two longitude lines to eliminate those horizontal lines. However I don't know the proj4 code to realize this.

Answer 1

Use the function nowrapSpatialPolygons at the anti-meridian of your central longitude. This doesn't work with wrld_simpl from maptools, but it does work with countriesLow from rworldmap.

library(rworldmap)
data(countriesLow)
library(maptools)
prj <- "+proj=robin +lon_0=-198 +x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs"
x0 <- nowrapSpatialPolygons(countriesLow, offset = -18)
x <- spTransform(x0, CRS(prj))
plot(x, col = colorRampPalette(c("yellow", "orange", "brown"))(length(x)))