1with(airpc, {
2pc  <- cbind(Comp.1, Comp.2)
3pc1 <- pc[Period==1,]
4pc2 <- pc[Period==2,]
5pc3 <- pc[Period==3,]
6xlim <- range(Comp.1)
7ylim <- range(Comp.2)
8
9par(mfrow=c(2,2))
10plot(Comp.1, Comp.2, xlim = xlim, ylim = ylim, main="1914-84")
11lines(xlim, c(0,0), lty=2)
12lines(c(0,0), ylim, lty=2)
13plot(pc1, xlim = xlim, ylim = ylim, main="1914-35")
14lines(xlim, c(0,0), lty=2)
15lines(c(0,0), ylim, lty=2)
16plot(pc2, xlim = xlim, ylim = ylim, main="1936-55")
17lines(xlim, c(0,0), lty=2)
18lines(c(0,0), ylim, lty=2)
19plot(pc3, xlim = xlim, ylim = ylim, main="1956-84")
20lines(xlim, c(0,0), lty=2)
21lines(c(0,0), ylim, lty=2)
22par(mfrow=c(1,1))
23})
24