Avoiding horizontal lines and crazy shapes when building maps in ggplot2

Question

I need a plot of an area, such as Latin America, using the world form file from IPUMSI ...

https://international.ipums.org/international/resources/gis/IPUMSI_world.zip

... I will add a few more IPUMS areas, so I really want to use this as my template layer.

I am having difficulty with the schedule when I add constraints via coord_map in ggplot2.

The source spatial file looks fine

 library("ggplot2") library("raster") sd0 <- readShapePoly("./IPUMSI_world.shp") df0 <- fortify(sd0) ggplot(data = df0, mapping = aes(x = long, y = lat, group = group)) + geom_polygon(fill = "black", colour = "black") 

When I want to focus on Latin America, I get some unwanted horizontal lines:

 ggplot(data = df0, mapping = aes(x = long, y = lat, group = group)) + geom_polygon(fill = "black", colour = "black") + coord_map(xlim = c(-125, -30), ylim = c(-60, 35)) 

I tried to fix this using clipPolys function following the instructions here

 library("PBSmapping") df1 <- df0 names(df1)[c(1,2,6,3)] <- c("X","Y","PID","POS") df1$PID <- as.numeric(df1$PID) df2 <- clipPolys(polys = df1, xlim = c(-125, -30), ylim = c(-60, 35), keepExtra = TRUE) names(df2)[names(df2)=="X"] <- "long" names(df2)[names(df2)=="Y"] <- "lat" names(df2)[names(df2)=="PID"] <- "id" ggplot(data = df2, mapping = aes(x = long, y = lat, group = group)) + geom_polygon(fill = "black", colour = "black") 

Not very happy with this story either. I thought this was a problem with holes, as in this question, but the proposed solution gives the same plots as above:

 gghole <- function(fort){ poly <- fort[fort$id %in% fort[fort$hole,]$id,] hole <- fort[!fort$id %in% fort[fort$hole,]$id,] out <- list(poly,hole) names(out) <- c('poly','hole') return(out) } ggplot(df2, aes(x=long, y=lat, group=group)) + geom_polygon(data = gghole(df2)[[1]], fill = "black", colour = "black") + geom_polygon(data = gghole(df2)[[2]], fill = "black", colour = "black") ggplot(df0, aes(x=long, y=lat, group=group)) + geom_polygon(data = gghole(df0)[[1]], fill = "black", colour = "black") + geom_polygon(data = gghole(df0)[[2]], fill = "black", colour = "black") + coord_map(xlim = c(-125, -30), ylim = c(-60, 35)) 

Answer 1

Another solution is to limit the view, and how to remove the point from the render:

 library(ggplot2) library(maptools) library(mapproj) # Maptools dataset data(wrld_simpl) world <- fortify(wrld_simpl) # Same plot, but restrict the view instead of removing points # allowing the complete render to happen ggplot(world, mapping = aes(x = long, y = lat, group = group)) + geom_polygon(fill = "black", colour = "black") + coord_cartesian(xlim = c(-125, -30), ylim = c(-60, 35)) 

Answer 2

You must delete data outside the chart area. So use scale_x/y_continuous to set limits instead of coord_map

 ggplot(data = df0, mapping = aes(x = long, y = lat, group = group)) + scale_x_continuous(limits = c(-125, -30)) + scale_y_continuous(limits = c(-60, 35)) + geom_polygon(fill = "black", colour = "black")