Mapping Global Earthquake using XML and Maptools

Everyday the US Geological Survey (USGS) publish earthquake data (http://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/quakes_all.html) all over the globe. Using XML and maptool packages of R I downloaded and map USGS earthquake data using the following codes :

library(XML)
usgseq<-"http://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/quakes_all.html"

weq1 = readHTMLTable(usgseq, header=T, which=1,stringsAsFactors=F)
weq2 = readHTMLTable(usgseq, header=T, which=2,stringsAsFactors=F)
weq3= readHTMLTable(usgseq, header=T, which=3,stringsAsFactors=F)
weq4 = readHTMLTable(usgseq, header=T, which=4,stringsAsFactors=F)
weq5 = readHTMLTable(usgseq, header=T, which=5,stringsAsFactors=F)
weq6 = readHTMLTable(usgseq, header=T, which=6,stringsAsFactors=F)
weq7 = readHTMLTable(usgseq, header=T, which=7,stringsAsFactors=F)
weq8 = readHTMLTable(usgseq, header=T, which=8,stringsAsFactors=F)

eq<-rbind(weq1,weq2,weq3,weq4,weq5,weq6,weq7,weq8)


weq<-eq[,c(2,4,5)]
x<-as.numeric(weq[,3])
y<-as.numeric(weq[,2])
z<-as.numeric(weq[,1])

library(maptools)
data(wrld_simpl)
plot(wrld_simpl, col=”green4″, border=”white”, axes=T)

plot(wrld_simpl, col=”green4″, border=”white”)
points(y~x, cex=(z^2)/12, col=ifelse(z>5,”red”,”blue”), pch=19)
text(0,101,”Global Earthquake Maps (May 15-23,2012)”, cex=1.8)
text(-180,-95,”Data Source: USGS\nCreated by: ARSalvacion”, adj=0, cex=0.5)