# esempio originale di Kerrich ------------------------------------------
kerrich <- c(4,10,17,21,25,29,32,35,40,44,98,146,199,255,312,368,413,
             458,502,1013,1510,2029,2533,3009,3516,4034,4538,5067)

k <- c(seq(10,90,10),seq(100,900,100),seq(1000,10000,1000))
y <- kerrich - k/2

# figura 5.7 ------------------------------------------------------------
plot(k,y,type="l",log="x")
abline(h=0,lty=2)
# -----------------------------------------------------------------------

y <- kerrich/k - 1/2

# figura 5.8 ------------------------------------------------------------
plot(k,y,type="l",log="x")
abline(h=0,lty=2)
# -----------------------------------------------------------------------