Incomplete geographic boundaries using geom_polygon to build a map - ggplot2

Question

I have a data frame with the coordinates of tweets, such as:

library(ggplot2) df <- data.frame(long = c(-58.1, -58.2, -58.3, -58.4, -58.5, -55), lat = c(-34.1, -34.2, -34.3, -34.4, -34.5, -25)) 

I would like to build a metropolis of Buenos Aires, known as AMBA. It is determined by the region: longitud: (-58, -59) latitude: (-34, -35)

I have a row in my data frame that is outside the scope of AMBA. (important for question (2))

Here is what I tried:

Download Argentina Map Information

 con <- url("http://gadm.org/data/rda/ARG_adm2.RData") print(load(con)) close(con) ggmap <- fortify(gadm, region = "NAME_2") 

Set limits for the schedule to include only AMBA

 lim <- data.frame(lon = c(-59, -58), lat = c(-35, -34)) 

Plot

 ggplot(data=ggmap, aes(x=long, y=lat)) + scale_x_continuous(limits = c(-59,-58)) + scale_y_continuous(limits = c(-35,-34)) + geom_polygon(data = ggmap, fill = "grey80", aes(group=group)) + geom_path(color="white",aes(group=group)) + geom_point(data = df, aes(x = lon, y = lat, colour = "red"), alpha = 30/100) 

QUESTIONS:

• The main problem is that the areas of political borders are not complete in foreign countries, so the map looks strange. Will there be a way around this?
• Do I have to multiply the data frame to save the observations inside the AMBA area or can I directly make a plot and select the area of ​​interest to me. I believe this is what scale_x_continuous (limits = ...) does.

Answer 1

Try coord_map instead of scale_x_continuous / scale_y_continuous . Setting limits in the coordinate system will increase the scale (for example, you look at it with a magnifying glass) and do not change the basic data, such as restrictions on the installation on the scale.

 ggplot(data=ggmap, aes(x=long, y=lat)) + geom_polygon(data=ggmap, fill="grey80", aes(group=group)) + geom_path(color="white",aes(group=group)) + geom_point(data=df, aes(x=long, y=lat), colour="red", alpha=30/100) + coord_map(xlim=-c(59, 58), ylim=-c(35,34))