r - Plot coordinates on map

Question

I am trying to plot my coordinates using R. I have tried already to follow different post (R: Plot grouped coordinates on world map ; Plotting coordinates of multiple points at google map in R) but I am not having much success with my data.

I am trying to achieve a flat map of the world with my gps coordinate as colored dots (each area a specific color):

area         lat    long
Agullhas    -38,31  40,96
Polar       -57,59  76,51
Tasmanian   -39,47  108,93

library(RgoogleMaps)
lat <- c(-38.31, -35.50) #define our map's ylim
lon <- c(40.96,37.50) #define our map's xlim
center = c(mean(lat), mean(lon))  #tell what point to center on
zoom <- 2 #zoom: 1 = furthest out (entire globe), larger numbers = closer in
terrmap <- GetMap(center=center, zoom=zoom, maptype= "satallite", destfile = "satallite.png")

problem that now I don't know how to add my points and I will like one color for each region.

Could anyone help me going forward with it?

the other option I have tried is :

library(maps)
library(mapdata)
library(maptools)
map(database= "world", ylim=c(-38.31, -35.5), xlim=c(40.96, 37.5), col="grey80", fill=TRUE, projection="gilbert", orientation= c(90,0,225))
lon <- c(-38.31, -35.5)  #fake longitude vector
lat <- c(40.96, 37.5)  #fake latitude vector
coord <- mapproject(lon, lat, proj="gilbert", orientation=c(90, 0, 225))  #convert points to projected lat/long
points(coord, pch=20, cex=1.2, col="red")  #plot converted points

but the coordinates ends in a wrong position and I am not sure why

Hope someone can help

Answer 1

As an alternative to RgoogleMaps, you can also use the combination ggplot2 with ggmap.

With this code:

# loading the required packages
library(ggplot2)
library(ggmap)

# creating a sample data.frame with your lat/lon points
lon <- c(-38.31,-35.5)
lat <- c(40.96, 37.5)
df <- as.data.frame(cbind(lon,lat))

# getting the map
mapgilbert <- get_map(location = c(lon = mean(df$lon), lat = mean(df$lat)), zoom = 4,
                      maptype = "satellite", scale = 2)

# plotting the map with some points on it
ggmap(mapgilbert) +
  geom_point(data = df, aes(x = lon, y = lat, fill = "red", alpha = 0.8), size = 5, shape = 21) +
  guides(fill=FALSE, alpha=FALSE, size=FALSE)

you get this result: