(This article was first published on

**Statistical Research » R**, and kindly contributed to R-bloggers)This is a brief example using the *maps* in R and to highlight a source of data. This is real-time data and it comes from the U.S. Geological Society. This shows the location of earthquakes with magnitude of at least 1.0 in the lower 48 states.

library(maps) library(maptools) library(rgdal) eq = read.table(file="http://earthquake.usgs.gov/earthquakes/catalogs/eqs7day-M1.txt", fill=TRUE, sep=",", header=T) plot.new() my.map <- map("state", interior = FALSE, plot=F) x.lim <- my.map$range[1:2]; x.lim[1] <- x.lim[1]-1; x.lim[2] <- x.lim[2]+1; y.lim <- my.map$range[3:4]; y.lim[1] <- y.lim[1]-1; y.lim[2] <- y.lim[2]+1; map("state", interior = FALSE, xlim=x.lim, ylim=y.lim) map("state", boundary = FALSE, col="gray", add = TRUE) title("Magnitude 1+ Earthquakes Over the Past 7 Days") eq$mag.size <- NULL eq$mag.size[eq$Magnitude>=1 & eq$Magnitude<2] <- .75 eq$mag.size[eq$Magnitude>=2 & eq$Magnitude<3] <- 1.0 eq$mag.size[eq$Magnitude>=3 & eq$Magnitude<4] <- 1.5 eq$mag.size[eq$Magnitude>=4] <- 2.0 eq$mag.col <- NULL eq$mag.col[eq$Magnitude>=1 & eq$Magnitude<2] <- 'blue' eq$mag.col[eq$Magnitude>=2 & eq$Magnitude<3] <- 'green' eq$mag.col[eq$Magnitude>=3 & eq$Magnitude<4] <- 'orange' eq$mag.col[eq$Magnitude>=4] <- 'red' points(x=eq$Lon,y=eq$Lat,pch=16,cex=eq$mag.size, col=eq$mag.col) eq$magnitude.text <- eq$Magnitude eq$magnitude.text[eq$Magnitude<4] <- NA text(x=eq$Lon,y=eq$Lat,col='black',labels=eq$magnitude.text,adj=c(2.5),cex=0.5) legend('bottomright',c('M 1-2','M 2-3','M 3-4','M4+'), ncol=2, pch=16, col=c('blue','green','orange','red')) box()

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