tmpar <- par(mar=c(1.5,0,0,0))

diam <- .2
tmp <- diam / sqrt(2)
tmp2 <- sqrt(2)
tmp3 <- 3*tmp2/2

plot(c(-diam,tmp3+diam),c(-diam,1+diam),type="n",xaxt="n",yaxt="n",
	xlab="",ylab="")

mtext("Split Plot",1,at=.25)

circle(0,.5,diam,cen=0)
text(0,.5,"subplot\nerror")

arrow(c(tmp,.5-tmp),c(.5+tmp,1-tmp),2)
circle(.5,1,diam,cen=0)
text(.5,1,"B")

arrow(c(tmp,.5-tmp),c(.5-tmp,tmp),2)
circle(.5,0,diam,cen=0)
text(.5,0,"A*B")

abline(v=(.5+tmp2)/2,lty=3)

mtext("Whole Plot",1,at=(tmp2+tmp3)/2)

arrow(c(diam,tmp2-diam),c(.5,.5),2,lty=2)
circle(tmp2,.5,diam,cen=0)
text(tmp2,.5,"plot\nerror")

arrow(c(tmp2+diam,tmp3-diam),c(.5,.5),2)
circle(tmp3,.5,diam,cen=0)
text(tmp3,.5,"A")

par(tmpar)