CODEWITHSUNDEEP
rpolygonggmap
JaElf
JaElf

Reputation: 3

Plot polygon with ggmap in R

I want to plot a Polygon in a map. For this I use ggmap at the moment, but it doesnt let me do it giving me always an error message:

Fehler: ggplot2 none-numeric argument for binary Operator

My code looks like this:

> library(rgdal)
> library(geojsonio)
> library(sp)
> library(maps)
> library(ggmap)
> library(maptools)

> data_file <- "/home/jan/Downloads/map.geojson"

> data_json <- geojson_read(data_file, what = "sp")

> plot(data_json, usePolypath = FALSE)

> mapImage <- ggmap(get_googlemap(c(lon = -118.243683, lat = 34.052235), scale = 1, 
+                                 zoom = 7), extent = "normal")
Map from URL : http://maps.googleapis.com/maps/api/staticmap?center=34.052235,-118.243683&zoom=7&size=640x640&scale=1&maptype=terrain&sensor=false

> dat <- as.data.frame(data_json)

> names(data)[1:2] <- c("lon","lat")

> print(mapImage)+
+   geom_polygon(data = dat, aes(lon, lat), colour="red", fill="red")

Fehler in print(mapImage) + geom_polygon(data = dat, aes(lon, lat), colour = "red",  : 
  nicht-numerisches Argument für binären Operator

but if I do 

> dat2 <- as.numeric(dat)

> print(mapImage)+
+   geom_polygon(data = dat2, aes(lon, lat), colour="red", fill="red")
Fehler: ggplot2 doesn't know how to deal with data of class numeric

I get the error

ggplot2 doesn't know how to deal with data of class numeric

PS. Iḿ very new to R and programming

Thank you

Upvotes: 0

Views: 1025

Answers (1)

Spacedman
Spacedman

Reputation: 94182

This:

data_json <- geojson_read(data_file, what = "sp")

returns an sp class object, which ggplot and geom_polygon can't deal with.

The fix is to run fortify on it to make a data frame that geom_polygon can use. You've not supplied us with your data file so we can't give you the exact code, but:

data_file <- system.file("examples", "california.geojson", package = "geojsonio")
data_json <- geojson_read(data_file, what = "sp")
fd = fortify(data_json)
mapImage + geom_polygon(data=fd, aes(x=long,y=lat))

should give you enough clues.

Upvotes: 1

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