Project 1 - figure 4

population_range = max(population$Change) - min(population$Change)
population$Normalized = (population$Change - min(population$Change)) / population_range
population$distinct_national = distinct_national$Normalized

ggplot(population, aes(Year)) + 
  geom_line(aes(y=distinct_national, color='blue')) +
  geom_line(aes(y=Normalized, color='red')) +
  scale_colour_manual("",
                   labels = c("Unique names", "Population"),
                   values = c("red", "blue")) +
  ggtitle('Number of unique names against population')