小编cai*_*ira的帖子

# Data

economy <- read.csv("data-economy.csv", header=TRUE)

# Convex hulls.

hulls <- ddply(economy, .(Latitude, Longitude), function(economy) 
            economy[chull(economy$Latitude, economy$Longitude), ])

fig <- ggplot(economy, aes(Latitude, Longitude, colour="black", fill="black")) + 
              geom_point() + 
              geom_density2d(alpha=.5) + 
              labs(x = "Latitude", y = "Longitude") + 
              geom_polygon(data=hulls, alpha=.2)

fig

X <- economy
chull(X)
plot(X, cex = 0.5)
hpts <- chull(X)
hpts <- c(hpts, hpts[1])
lines(X[hpts, ])