---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- # The area of the Italian peninsula T = read.table("http://macosa.dima.unige.it/R/penisola.txt",skip=1,sep=",") X = T$V1; Y = T$V2 HF=4; BF=4 Plane(min(X),max(X), min(Y),max(Y)); polyC(X,Y, "cyan") # The area using as a unit of measure the "squares" delimited by longitudes and # latitudes area = areaPol(X,Y); area # 28.59358 # Its transformation into km^2 taking into account that 1 degree of latitude is 111 km # (rounded value) and 1 degree of longitude in Italy is approximately 79 km (it is 82 # km at Napoli): Area = area*111*79; round(Area,-3) # 250737.1 251000 # Or: signif(Area, 3) # 251000 # The area of the Italian peninsula is actually 252000 km^2 # # The Italian peninsula with a scale showing (approximately) the kilometers (and the # distances from the centroid): X1=X*79; Y1=Y*111 BF <- 4; HF <- 4; PLANE(min(X1),max(X1), min(Y1),max(Y1)); polyline(X1,Y1, "blue") C <- centerPol(X1,Y1); C; POINT(C[1],C[2],"red") # 963.0065 4827.3143 circl(C[1],C[2],200,"brown") circl(C[1],C[2],400,"brown") circl(C[1],C[2],600,"brown") segm(1200,4800,1300,4800,"brown") POINT(1200,4800,"brown"); POINT(1300,4800,"brown") text(1250,4850,"100 km") Other examples of use