Multiple Y-axis in a R plot

I often have to to plot multiple time-series with different scale of values for comparative purposes, and although placing them in different rows are useful, placing on a same graph is still useful sometimes…
I searched a bit about this, and found some nice suggestions for 2 Y-axis, but haven’t found anything for more 2+. So here’s my solution:



#Create Dataset

time<-seq(7000,3400,-200)
pop<-c(200,400,450,500,300,100,400,700,830,1200,400,350,200,700,370,800,200,100,120)
grp<-c(2,5,8,3,2,2,4,7,9,4,4,2,2,7,5,12,5,4,4)
med<-c(1.2,1.3,1.2,0.9,2.1,1.4,2.9,3.4,2.1,1.1,1.2,1.5,1.2,0.9,0.5,3.3,2.2,1.1,1.2)


#Define Margins. The trick is to use give as much space possible on the left margin (second value)
par(mar=c(5, 12, 4, 4) + 0.1)

#Plot the first time series. Notice that you don’t have to draw the axis nor the labels

plot(time, pop, axes=F, ylim=c(0,max(pop)), xlab=””, ylab=””,type=”l”,col=”black”, main=””,xlim=c(7000,3400))
points(time,pop,pch=20,col=”black”)
axis(2, ylim=c(0,max(pop)),col=”black”,lwd=2)
mtext(2,text=”Population”,line=2)






par(new=T)
plot(time, med, axes=F, ylim=c(0,max(med)), xlab=””, ylab=””, 
type=”l”,lty=2, main=””,xlim=c(7000,3400),lwd=2)
axis(2, ylim=c(0,max(med)),lwd=2,line=3.5)
points(time, med,pch=20)
mtext(2,text=”Median Group Size”,line=5.5)


#Plot the third time series. Again the line parameter are both further increased.


par(new=T)
plot(time, grp, axes=F, ylim=c(0,max(grp)), xlab=””, ylab=””, 
type=”l”,lty=3, main=””,xlim=c(7000,3400),lwd=2)
axis(2, ylim=c(0,max(grp)),lwd=2,line=7)

points(time, grp,pch=20)
mtext(2,text=”Number of Groups”,line=9)

#We can now draw the X-axis, which is of course shared by all the three time-series.

axis(1,pretty(range(time),10))
mtext(“cal BP”,side=1,col=”black”,line=2)

#And then plot the legend.

legend(x=7000,y=12,legend=c(“Population”,”Median Group Size”,”Number of Groups”),lty=c(1,2,3))