Plotting the coordinates of several points on a google map in R

Question

I wanted to build coordinates on a Google map with a point identifier:

Sample data:

coordinates id 1 (7.1735, 45.8688) 2 2 (7.17254, 45.8689) 3 3 (7.17164, 45.8692) 4 4 (7.18018, 45.8716) 5 5 (7.17807, 45.8701) 6 6 (7.17723, 45.8692) 7 7 (7.17524, 45.8681) 8 8 (7.18141, 45.8718) 9 9 (7.1793, 45.8702) 10 10 (7.17836, 45.8707) 11 11 (7.17519, 45.8697) 12 12 (7.17938, 45.8708) 13 13 (7.17551, 45.8693) 14 14 (7.17684, 45.8694) 15 15 (7.18099, 45.8726) 17 16 (7.18015, 45.8725) 18 17 (7.18122, 45.8736) 19 18 (7.17491, 45.8692) 20 19 (7.15497, 45.8706) 25 20 (7.1534, 45.8695) 28 21 (7.15265, 45.8699) 29 22 (7.15442, 45.87) 31 23 (7.1561, 45.8698) 32 24 (7.184, 45.896) GSBi_1 25 (7.36, 45.901) GSBi__1 26 (7.268, 45.961) GSBj__1 27 (7.276, 45.836) GSBj_1 28 (7.272, 45.899) GSB 29 (7.16667, 45.8667) GSB_r 

Answer 1

Instead of requesting a Switzerland map from Google, you should request a map of a specific location by specifying the longitude / latitude and the desired scale (and possibly scale). Then you do not have to use coord_map() and blur the image.

Here are the basics, you can play with colors and sizes, as in any ggplot:

 library(ggplot2) library(ggmap) # copying text off screen # since the OP did not use dput() data<-read.table("clipboard") # reformat data=data[,-1] names(data)=c("lon","lat","id") data$lon <- as.numeric(gsub('[\\(\\)\\,]', '', data$lon)) data$lat <- as.numeric(gsub('[\\(\\)\\,]', '', data$lat)) head(data) # lon lat id # 1 7.17350 45.8688 2 # 2 7.17254 45.8689 3 # 3 7.17164 45.8692 4 # etc # determine a reasonable center for map, # this could fail in some places (near poles, 180th meridian) # also google appears to shift things slightly center = paste(min(data$lat)+(max(data$lat)-min(data$lat))/2, min(data$lon)+(max(data$lon)-min(data$lon))/2, sep=" ") # get map image from google map <- get_map(location = center, zoom = 11, maptype = "terrain", source = "google") # start a ggplot. it won't plot til we type p p <- ggmap(map) # add text labels, these will overlap p <- p + geom_text(data=data,aes(x = lon, y = lat, label = id), colour="white",size=4,hjust=0, vjust=0)+ theme(legend.position = "none") # add points last so they are on top p <- p + geom_point(data=data,aes(x=lon, y=lat),colour="white",size=2) # display plot p 

This is naturally described in ?get_map and ?get_googlemap .

Answer 2

One of the problems with plotting your points is that if you use zoom=10 in the get_map() function, then your points are outside the map and they want to be built, so I used zoom=5 instead.

  library(ggmap) map <- get_map(location = 'Switzerland', zoom = 5, maptype = "terrain", source = "google") 

To build the map, I used the ggmap() function. You can add geom_point() points. For this, your data samples were saved as a df data frame with columns x , y and id . You can use coord_map() to get closer to the points.

  p <- ggmap(map) p <- p +geom_point(data=df,aes(x=x,y=y))+ coord_map(xlim=c(7,8),ylim=c(45.5,46)) print(p) 

If you need to add labels to each point, add this line to map p

 annotate("text",x=df$x,y=df$y,label=df$id)