R语言如何让坐标轴在原点交汇

x = seq(-3, 3, 0.01)

y1 = 2^x

y2 = 2^(-x)

par(mar=c(2,2,2,2),las=1)

xlim<-c(-4.5,4.5)

ylim<-c(-1,8.5)

plot(x,y1,type=’n’,xlim=xlim,ylim=ylim,axes=F)

lines(x, y1, type = “l”, col = “blue”)

lines(x, y2, type = “l”,col = “red”)

axis(2,at=0:9,labels=c(NA,1:9),pos=0)

axis(1,at=-5:5,labels=-5:5,pos=0)