t = seq( 0, +9, length.out=1000 )
f = rep( 0, length(t) )

f[ (3 <= t) & (t < 5) ] = -2
f[ (5 <= t) & (t < 7) ] = 2
f[ (7 <= t) ] = 1

#postscript("../../WriteUp/Graphics/Chapter6/chap_6_sect_3_prob_7_plot.eps", onefile=FALSE, horizontal=FALSE)
plot( t, f, type='p', cex=0.25, pch=20, col='black' )
points( c(0, 3, 5, 7), c(0, -2, 2, 1), pch=20, col='black', cex=1.5 )
grid()
#dev.off()