Din.grafo = function (X,f,r=2,
  cex=0.5,lwd=0.3,punta=0.2)

{n=length(X);
t=seq(0,length=n,by=2*pi/n);
centri=round(Gf.cerchio(t,r),2)

t=seq(0,2*pi,by=0.01)
cerchio=Gf.cerchio(t,0.2)

for (k in 1:n)
{polygon(cerchio+centri[k],col="yellow");
text(Re(centri[k]),Im(centri[k]),
  X[k],cex=cex)}

par(lwd=lwd)
for (x in X) {y=f(x); if (y!=x)
R=Gdf.mezzo(centri[match(x,X)],
  centri[match(y,X)],
  punta=punta,d1=0.2,d2=0.2)}}

X=c(4,6,7,8,2,5,1,3)
f = function (x) P.quale(x,1,3,2,8,3,3,4,7,
  5,1,6,7,7,8,8,3)

Gs.postscript("06-dingrafo-2.ps",4.8,4.8)
lato=c(-2.4,2.4); par(bg="#ccff99")
Gd.grafica(lato,lato,cornice=T)
Din.grafo(X,f)
dev.off()