tmpar <- par( mar = c(3,3,.5,.5), mfrow = c(1,2) )
on.exit( { par( tmpar ); rm( tmpar, tmp ) } )

tmp <- order( apply( ran, 2, median ) )
boxplot( as.list( ran[ , tmp ] ) )
#axis( 1, tmp, names( ran ) )
mtext( "(a) box-plots by class", 1, 2 )

plot( c(0.5,3.5), range( ran ), type = "n",
   xaxt = "n", xlab = "", ylab = "" )
mtext( c("mean","class","element"), 1, 0.5, at = 1:3 )
mtext( "(b) tree diagram", 1, 2 )
mtext( "response", 2, 2 )
points( 1, ran.mean )
points( rep( 2, length( ran ) ), ran.class )
points( rep( 3, length( unlist( ran ) ) ), unlist( ran ) )
branch( ran.mean, ran.class, 1:2, flip = T )
for ( i in names( ran ) )
   branch( mean( ran[[i]] ), ran[[i]], 2:3, flip = T )