How do I add circle to 'wifi zone' plot?

Question

I'm a university student, and r programming beginner. I have a problem when study 'ggplot2' package.

I want plot 'wifi zone' and add circles to a plot, but i cannot do.. and puzzled about what to do..

and I want to know point_geom size that correspond to "wifi zone" real radius '20 meters'.

Data contains latitude, longitude of spot and about what kind of mobile agency is servicing.

My codes as follows :

library(ggmap)

wifi_daejeon <- read.csv("C:/Users/Byeongsoo/Desktop/R markdown/대전와이파이.csv")
wifi_gungdong <- subset(wifi_daejeon, EMD_NM == "궁동")
cent_gungdong <- c(mean(wifi_gungdong$LON), mean(wifi_gungdong$LAT))
bmap_gungdong <- ggmap(get_googlemap(center = cent_gungdong, zoom = 15, maptype = "roadmap"), 
                       extent = "device", 
                       base_layer = ggplot(wifi_gungdong, aes(x = LON, y = LAT, colour = CCB)))
bmap_gungdong + 
  geom_point() + 
  theme(plot.title = element_text(size = 20, colour = "BLUE"), 
  axis.text = (element_text(size=10))) +  
  theme(legend.title = element_text(size = 15)) +
  theme()

unfortunately, i can't upload image, because i don't have 10 reputation..

image's URL is :

http://postfiles4.naver.net/20140318_99/soccerball1_1395130002602k7k10_PNG/%C4%B8%C3%B3.PNG?type=w3

This has been my Question. Thank you for reading up to now.

Answer 1

map <- get_map()
g<-ggmap(map, extent = TRUE)
g + geom_point(aes(x=-95.36327,y=29.763284),col='red',size=20,shape=1)