CODEWITHSUNDEEP
rggplot2stackrnaturalearthggspatial
nobody
nobody

Reputation: 146

R ggplot and exceeding stack size

I am using R to display some polygons on a map. Polygons are stored in a geoJson file and there are many of them (around 1000). In some geojson files may be even much more.

Here is the R program reading the geojson file and drawing polygons on a map:

library ("ggplot2")
library ("sf")
library ("rnaturalearth")
library ("rnaturalearthdata")
library ("ggspatial")
library ("geojsonR")

europe <- ne_countries (continent = "europe", scale = "medium", returnclass = "sf")
class (europe)

p <- ggplot (data = europe)
p <- p + geom_sf ()

js <- FROM_GeoJson (url_file_string = "file.geojson")

i <- 0
for (f in js$features) {
    if (!is.null (f$properties$InterferenceLevel)) {
        if (i < 250) {
            #print (f$properties$InterferenceLevel)
            #print (f$geometry$coordinates)
            overlay_polygon <- f$geometry$coordinates
            overlay_polygon <- sf::st_polygon (list(f$geometry$coordinates))
            #print (overlay_polygon)
            poly <- sf::st_as_sfc (list (overlay_polygon), crs = 4326)

            p <- p + geom_sf (data = poly, fill=alpha ("red", 0.2), color=alpha ("red", 0.2))
        }
        i <- i + 1
        #print (i)
    }
}

p <- p + coord_sf(xlim = c(-20, 42), ylim = c(35, 72))
plot (p)

The problem I have is that if I want to draw all polygons in that way, the program stops and reports

Error: C stack usage  7970756 is too close to the limit

I have added another condition involving a counter to see how many polygons I can draw. At 250 the map is shown. If I go higher, I get the error message.

Does anybody has an idea of another way to draw transparent polygons over the map in a way that does not fill up the stack size? I do not have much experience with ggplot. I have been using charts with tens of thousands of dots without problems and here I cannot draw more than a couple of hundreds polygons. I am sure there is a way to do it. I just don't know how to add them to the map once it is shown in a window. It does not have to be ggplot if it can be done with some other function.

Upvotes: 0

Views: 51

Answers (1)

Spacedman
Spacedman

Reputation: 94182

Its not sf as such, you can't have so many items in a ggplot. This loop adds a single data point using geom_point and prints a counter until it falls over:

p = ggplot()
i = 1
while(TRUE){
 p = p + geom_point(data=data.frame(x=runif(1),y=runif(1)),aes(x=x,y=y))
 message(i);i=i+1
}

For me this runs until 878 and then I get Error: C stack usage 7974740 is too close to the limit

Solution is to amass your data into a single data frame and add it with one geom_ call.

If you need to colour or style them in some way, keep that in the data frame too, and specify that attribute not as an aes() but as a vector parameter, eg:

geom_sf(all_my_polys, col=all_my_polys$colour)

Upvotes: 4

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