Digital Scotland: Fig. 1.5

Deprivation in Scotland has a far more significant effect on broadband uptake than geography or connection speeds.

This figure shows how the proportion of households offline varies with median connection speed for each decile of (each 10% of the population ordered by) SIMD deprivation. Once we allow for the effects of deprivation, we can see that uptake generally increases where speeds are lower. In deciles 5-9 we see lower uptake where speeds are poor (< 4 Mb/s).

We use the model dataset, and fit the two parameters of a beta-binomial distribution, as smooth functions of isolation, using a generalised additive model, provided by the VGAM package in R. The lines are drawn using the following code:

with(model,
     for (q in levels(decile)){
         m <- subset(model,
                     decile == q & !is.na(medspeed))
         speedgam <-
             vgam(formula =
                  cbind(offline,
                        connected)
                  ~ s(medspeed,df=4),
                  family = betabinomial.ab,
                  data = m,
                  trace = TRUE,
                  )
         lines(test$medspeed,
               predict(speedgam,
                       type="response",
                       newdata=test),
               lwd=0.5)
         symbols(m$medspeed,
                 predict(speedgam,type="response"),
                 circles=sqrt(m$Household_Count),
                 inches=0.1,
                 fg=alpha(ur6pal[m$UrbRur6_2011_2012],0.2),
                 bg=alpha(ur6pal[m$UrbRur6_2011_2012],0.2),
                 add=T)
         text(32,
              predict(speedgam,
                      type="response",
                      newdata=data.frame(medspeed=31)),
              labels= c(q),adj=c(0,0.6))
     }
     )