Q1

For the following series,

  • Victorian Electricity Demand from vic_elec.
  1. Make a graph of the data. Do we need a transformation?
vic_elec %>% autoplot(Demand)

The variance looks like it might be decreasing over time so we should look into a transformation. But the variance doesn’t look like it changes much.

  1. Use box_cox() to do a log transformation. Discuss the result.
vic_elec %>% 
  autoplot(box_cox(Demand,0))

The variance looks the same as above. We should find the best lambda to use.

  1. Use Guerrero’s method to find the appropriate transformation.
features(vic_elec,Demand,features = guerrero)
## # A tibble: 1 x 1
##   lambda_guerrero
##             <dbl>
## 1          0.0999

As we can see from above the best lambda value is roughly equal to 0.01.