Tag Archives: plotGoogleMaps

How Big Is The Vatican City?

Curiosities, Maps, Simulation, , , , , , , ,

Dici che il fiume trova la via al mare e come il fiume giungerai a me (Miss Sarajevo, U2)

One way to calculate approximately the area of some place is to circumscribe it into a polygon of which you know its area. After that, generate coordinates inside the polygon and count how many of them fall into the place. The percentage of coordinates inside the place by the area of the polygon is an approximation of the desired area.

I applied this technique to calculate the area of the Vatican City. I generated a squared grid of coordinates around the Capella Sistina (located inside the Vatican City). To calculate the area I easily obtain the convex hull polygon of the coordinates using chull function of grDevices package. Then, I calculate the area of the polygon using areaPolygon function of geosphere package.

To obtain how many coordinates of the grid fall inside the Vatican City, I use revgeocode function of ggmap package (I love this function). For me, one coordinate is inside the Vatican City if its related address contains the words “Vatican City”.

What happens generating a grid of 20×20 coordinates? I obtain that the area of the Vatican City is about 0.32Km2 but according to Wikipedia, the area is 0.44Km2: this method underestimates the area around a 27%. But why? Look at this:

Vatican2

This plot shows which addresses of the grid fall inside the Vatican City (ones) and which of them do not fall inside (zeros). As you can see, there is a big zone in the South, and a smaller one in the North of the city where reverse geocode do not return “Vatican City” addresses.

Maybe Pope Francis should phone Larry Page and Sergey Brin to claim this 27% of his wonderful country.

I was willing to do this experiment since I wrote this post. This is the code:

require(geosphere)
require(ggmap)
require(plotGoogleMaps)
require(grDevices)
setwd("YOUR-WORKING-DIRECTORY-HERE")
#Coordinates of Capella Sistina
capella=geocode("capella sistina, Vatican City, Roma")
#20x20 grid of coordinates around the Capella
g=expand.grid(lon = seq(capella$lon-0.010, capella$lon+0.010, length.out=20),
lat = seq(capella$lat-0.005, capella$lat+0.005, length.out=20))
#Hull Polygon containing coordinates
p=g[c(chull(g),chull(g)[1]),]
#Address of each coordinate of grid
a=apply(g, 1, revgeocode)
#Estimated area of the vatican city
length(grep("Vatican City", a))/length(a)*areaPolygon(p)/1000/1000
s=cbind(g, a)
s$InOut=apply(s, 1, function(x) grepl('Vatican City', x[3]))+0
coordinates(s)=~lon+lat
proj4string(s)=CRS('+proj=longlat +datum=WGS84')
ic=iconlabels(s$InOut, height=12)
plotGoogleMaps(s, iconMarker=ic, mapTypeId="ROADMAP", legend=FALSE)

Going Bananas #1: Superman Was Born In Kentucky!

Going Bananas, , , , , , , ,

Who knows? Could be the tropic heat or something that I eat, that makes me gonzo (I’m Going Bananas, Madonna)

This is the first post of a new category called “Going Bananas” in which I will post totally crazy experiments. My aim is to try some techniques without taking care of making serious things. These are experiments without rhyme or reason (or, as we say in Spanish, sin pies ni cabeza). So here we go.

Some days ago, my friend Juanjo show me how to download a webpage and to extract a table in R. He did an amazing script to locate on a map all spanish football stadiums in just a handful of lines. And this is what what I will do in this experiment with a slight difference. I will not locate stadiums: I will try to locate the 118 chemical elements discovered up today. How to do it? It is extremely easy: as I did it in this previous post, using geocode function of ggmap package you can locate any address, even if it is the name of a chemical element.

It must be taking into account that almost all names of the elements come from greek or from latin as you can see here. This is the result of locating in the world the 118 chemical elements:

Bananas01

Some conclusions:

  • Only 88 elements (a 75%) have a place on Earth.
  • 40 of the elements with a place on Earth (a 45%) are located in the United States of America, very far from Greek-Latin cultures, by the way
  • Only 16 of them are located in Europe (a 16%)
  • South-Africa and Philipines have almost all the elements outside of EEUU and Europe.
  • And last but not least, Krypton is in Kentucky, as you can see here:

Bananas02

Clark Kent, Krypton, Kentucky … there are a lot of misteries surrounding Superman … and a lot of K letters!!!!

library(RCurl)
library(XML)
library(ggmap)
library (plotGoogleMaps)
webpage=getURL("http://en.wikipedia.org/wiki/List_of_elements", .opts = opts)
table=readHTMLTable(webpage)[[1]]
table=table[nchar(as.character(table$Element))>2,c("Sym", "Element")]
for (i in 1:nrow(table)) {
 valor=geocode(as.character(table$Element[i]))
 table$lon[i]=valor$lon;table$lat[i]=valor$lat}
table2paint=na.omit(table[, c("lat", "lon", "Sym", "Element")])
coordinates(table2paint)=~lon+lat
proj4string(table2paint)=CRS('+proj=longlat +datum=WGS84')
plotGoogleMaps(table2paint, col="yellow", control.width="0%", control.height="0%", mapTypeId='ROADMAP', legend=FALSE)