person_entropy.R

library(babynames)
library(dplyr)
library(ggplot2)

lifetables %>%
  mutate(decade = year)%>%
  group_by(decade)%>%
  mutate(prob_alive = lx/100000,
         study_year = year + x)->prob_people

births %>% 
  mutate(decade = floor(year/10)*10)%>%
  group_by(decade) %>%
  summarise(births = median(births))->decade_births


entropy <- function(probs){
  sum(probs * log2(1/probs), na.rm = T)
}

prob_people%>%left_join(decade_births)%>% filter(!is.na(births))%>%
  mutate(people = (births/2) * prob_alive)%>%
  group_by(study_year)%>%
  mutate(prob_person = people/sum(people))%>%
  summarise(entropy = entropy(prob_person))%>%
  ggplot(aes(study_year, entropy))+
    geom_line()